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<a href="log_8hpp.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno">    1</span><span class="comment">/* Flow</span></div>
<div class="line"><a id="l00002" name="l00002"></a><span class="lineno">    2</span><span class="comment"> * Copyright 2023 Akamai Technologies, Inc.</span></div>
<div class="line"><a id="l00003" name="l00003"></a><span class="lineno">    3</span><span class="comment"> *</span></div>
<div class="line"><a id="l00004" name="l00004"></a><span class="lineno">    4</span><span class="comment"> * Licensed under the Apache License, Version 2.0 (the</span></div>
<div class="line"><a id="l00005" name="l00005"></a><span class="lineno">    5</span><span class="comment"> * &quot;License&quot;); you may not use this file except in</span></div>
<div class="line"><a id="l00006" name="l00006"></a><span class="lineno">    6</span><span class="comment"> * compliance with the License.  You may obtain a copy</span></div>
<div class="line"><a id="l00007" name="l00007"></a><span class="lineno">    7</span><span class="comment"> * of the License at</span></div>
<div class="line"><a id="l00008" name="l00008"></a><span class="lineno">    8</span><span class="comment"> *</span></div>
<div class="line"><a id="l00009" name="l00009"></a><span class="lineno">    9</span><span class="comment"> *   https://www.apache.org/licenses/LICENSE-2.0</span></div>
<div class="line"><a id="l00010" name="l00010"></a><span class="lineno">   10</span><span class="comment"> *</span></div>
<div class="line"><a id="l00011" name="l00011"></a><span class="lineno">   11</span><span class="comment"> * Unless required by applicable law or agreed to in</span></div>
<div class="line"><a id="l00012" name="l00012"></a><span class="lineno">   12</span><span class="comment"> * writing, software distributed under the License is</span></div>
<div class="line"><a id="l00013" name="l00013"></a><span class="lineno">   13</span><span class="comment"> * distributed on an &quot;AS IS&quot; BASIS, WITHOUT WARRANTIES OR</span></div>
<div class="line"><a id="l00014" name="l00014"></a><span class="lineno">   14</span><span class="comment"> * CONDITIONS OF ANY KIND, either express or implied.</span></div>
<div class="line"><a id="l00015" name="l00015"></a><span class="lineno">   15</span><span class="comment"> * See the License for the specific language governing</span></div>
<div class="line"><a id="l00016" name="l00016"></a><span class="lineno">   16</span><span class="comment"> * permissions and limitations under the License. */</span></div>
<div class="line"><a id="l00017" name="l00017"></a><span class="lineno">   17</span><span class="comment"></span> </div>
<div class="line"><a id="l00018" name="l00018"></a><span class="lineno">   18</span><span class="comment">/// @file</span></div>
<div class="line"><a id="l00019" name="l00019"></a><span class="lineno">   19</span><span class="comment"></span><span class="preprocessor">#pragma once</span></div>
<div class="line"><a id="l00020" name="l00020"></a><span class="lineno">   20</span> </div>
<div class="line"><a id="l00021" name="l00021"></a><span class="lineno">   21</span><span class="preprocessor">#include &quot;<a class="code" href="log__fwd_8hpp.html">flow/log/log_fwd.hpp</a>&quot;</span></div>
<div class="line"><a id="l00022" name="l00022"></a><span class="lineno">   22</span><span class="preprocessor">#include &quot;<a class="code" href="detail_2log__fwd_8hpp.html">flow/log/detail/log_fwd.hpp</a>&quot;</span></div>
<div class="line"><a id="l00023" name="l00023"></a><span class="lineno">   23</span><span class="preprocessor">#include &quot;<a class="code" href="thread__lcl__str__appender_8hpp.html">flow/log/detail/thread_lcl_str_appender.hpp</a>&quot;</span></div>
<div class="line"><a id="l00024" name="l00024"></a><span class="lineno">   24</span><span class="preprocessor">#include &quot;<a class="code" href="util_2util_8hpp.html">flow/util/util.hpp</a>&quot;</span></div>
<div class="line"><a id="l00025" name="l00025"></a><span class="lineno">   25</span><span class="preprocessor">#include &quot;<a class="code" href="util_2detail_2util_8hpp.html">flow/util/detail/util.hpp</a>&quot;</span></div>
<div class="line"><a id="l00026" name="l00026"></a><span class="lineno">   26</span><span class="preprocessor">#include &quot;<a class="code" href="uniq__id__holder_8hpp.html">flow/util/uniq_id_holder.hpp</a>&quot;</span></div>
<div class="line"><a id="l00027" name="l00027"></a><span class="lineno">   27</span><span class="preprocessor">#include &lt;chrono&gt;</span></div>
<div class="line"><a id="l00028" name="l00028"></a><span class="lineno">   28</span><span class="preprocessor">#include &lt;string&gt;</span></div>
<div class="line"><a id="l00029" name="l00029"></a><span class="lineno">   29</span><span class="preprocessor">#include &lt;typeinfo&gt;</span></div>
<div class="line"><a id="l00030" name="l00030"></a><span class="lineno">   30</span> </div>
<div class="line"><a id="l00031" name="l00031"></a><span class="lineno">   31</span><span class="comment">// Macros.  These (conceptually) belong to the flow::log namespace (hence the prefix for each macro).</span></div>
<div class="line"><a id="l00032" name="l00032"></a><span class="lineno">   32</span><span class="comment"></span> </div>
<div class="line"><a id="l00033" name="l00033"></a><span class="lineno">   33</span><span class="comment">/**</span></div>
<div class="line"><a id="l00034" name="l00034"></a><span class="lineno">   34</span><span class="comment"> * Logs a WARNING message into flow::log::Logger `*get_logger()` with flow::log::Component `get_log_component()`, if</span></div>
<div class="line"><a id="l00035" name="l00035"></a><span class="lineno">   35</span><span class="comment"> * such logging is enabled by that `Logger`.  Supplies context information</span></div>
<div class="line"><a id="l00036" name="l00036"></a><span class="lineno">   36</span><span class="comment"> * to be potentially logged with message, like current time, source file/line/function,</span></div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno">   37</span><span class="comment"> * and thread ID/nickname info, in addition to the message, component, and severity.</span></div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno">   38</span><span class="comment"> * The severity checked against (and potentially logged in its own right) is flow::log::Sev:S_WARNING.</span></div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno">   39</span><span class="comment"> *</span></div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno">   40</span><span class="comment"> * More precisely, checks whether logging warnings is currently enabled in the `Logger*` returned by</span></div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno">   41</span><span class="comment"> * `get_logger()` in the macro invocation&#39;s context; if not does nothing; if so constructs and logs the</span></div>
<div class="line"><a id="l00042" name="l00042"></a><span class="lineno">   42</span><span class="comment"> * message as a warning via FLOW_LOG_WITHOUT_CHECKING().  Also, if `get_logger()` is null, then the effect is</span></div>
<div class="line"><a id="l00043" name="l00043"></a><span class="lineno">   43</span><span class="comment"> * the same as a `get_logger()-&gt;should_log()` returning `false` (meaning it is a no-op).</span></div>
<div class="line"><a id="l00044" name="l00044"></a><span class="lineno">   44</span><span class="comment"> *</span></div>
<div class="line"><a id="l00045" name="l00045"></a><span class="lineno">   45</span><span class="comment"> * `get_logger()` must exist, and if not null then `get_logger()` (returning</span></div>
<div class="line"><a id="l00046" name="l00046"></a><span class="lineno">   46</span><span class="comment"> * `Logger*`) and `get_log_component()` (returning `const Component&amp;`)</span></div>
<div class="line"><a id="l00047" name="l00047"></a><span class="lineno">   47</span><span class="comment"> * must return a valid pointer and reference to `Logger` and `Component`, respectively.</span></div>
<div class="line"><a id="l00048" name="l00048"></a><span class="lineno">   48</span><span class="comment"> * Most of the time these are available due to most logging code being in classes deriving from flow::log::Log_context</span></div>
<div class="line"><a id="l00049" name="l00049"></a><span class="lineno">   49</span><span class="comment"> * which supplies those methods and takes (at construction) the values to return subsequently.</span></div>
<div class="line"><a id="l00050" name="l00050"></a><span class="lineno">   50</span><span class="comment"> * In situations where this is impossible (such as `static` members methods or in free functions) or insufficient (such</span></div>
<div class="line"><a id="l00051" name="l00051"></a><span class="lineno">   51</span><span class="comment"> * as when one wants to use a different component vs. the one returned by flow::log::Log_context::get_log_component()),</span></div>
<div class="line"><a id="l00052" name="l00052"></a><span class="lineno">   52</span><span class="comment"> * use FLOW_LOG_SET_CONTEXT().</span></div>
<div class="line"><a id="l00053" name="l00053"></a><span class="lineno">   53</span><span class="comment"> *</span></div>
<div class="line"><a id="l00054" name="l00054"></a><span class="lineno">   54</span><span class="comment"> * ### Final log output subleties ###</span></div>
<div class="line"><a id="l00055" name="l00055"></a><span class="lineno">   55</span><span class="comment"> * We assume for this discussion that the notion of order of final output (to device/file/network/whatever) exists,</span></div>
<div class="line"><a id="l00056" name="l00056"></a><span class="lineno">   56</span><span class="comment"> * and that the `get_logger()` indeed safely outputs message M1 entirely before M2, or vice versa, for every</span></div>
<div class="line"><a id="l00057" name="l00057"></a><span class="lineno">   57</span><span class="comment"> * pair of messages (in this context by message we mean message+metadata pair) ever passed to `do_log()`.  With that</span></div>
<div class="line"><a id="l00058" name="l00058"></a><span class="lineno">   58</span><span class="comment"> * assumption in effect (IF indeed it is):</span></div>
<div class="line"><a id="l00059" name="l00059"></a><span class="lineno">   59</span><span class="comment"> *   - In a given thread T, and assuming the same `get_logger()`, if `FLOW_LOG_*(M1);`</span></div>
<div class="line"><a id="l00060" name="l00060"></a><span class="lineno">   60</span><span class="comment"> *     is called before `FLOW_LOG_*(M2);`, and both are successfully output by logger, then the final output order must</span></div>
<div class="line"><a id="l00061" name="l00061"></a><span class="lineno">   61</span><span class="comment"> *     have M1 precede M2, not vice versa.</span></div>
<div class="line"><a id="l00062" name="l00062"></a><span class="lineno">   62</span><span class="comment"> *     - In addition, assuming monotonically increasing time stamps, as time flows (which is the case most of the time</span></div>
<div class="line"><a id="l00063" name="l00063"></a><span class="lineno">   63</span><span class="comment"> *       with exceptions due to computer-clock adjustments and similar), M1&#39;s time stamp will be earlier (ignoring</span></div>
<div class="line"><a id="l00064" name="l00064"></a><span class="lineno">   64</span><span class="comment"> *       rounding) than M2&#39;s.</span></div>
<div class="line"><a id="l00065" name="l00065"></a><span class="lineno">   65</span><span class="comment"> *   - If, instead, M1 is logged in thread T1, while M2 is logged in thread T2:</span></div>
<div class="line"><a id="l00066" name="l00066"></a><span class="lineno">   66</span><span class="comment"> *     - If the 2 `FLOW_LOG_*()` calls are chronologically disjoint, then again the final output must also have</span></div>
<div class="line"><a id="l00067" name="l00067"></a><span class="lineno">   67</span><span class="comment"> *       M1 precede M2 if M1 went first; and vice versa.</span></div>
<div class="line"><a id="l00068" name="l00068"></a><span class="lineno">   68</span><span class="comment"> *       - Time stamps (under a well behaved clock again), again, will match this order.</span></div>
<div class="line"><a id="l00069" name="l00069"></a><span class="lineno">   69</span><span class="comment"> *     - If the 2 `FLOW_LOG_*()` calls chronologically overlap, then either final output order is possible.</span></div>
<div class="line"><a id="l00070" name="l00070"></a><span class="lineno">   70</span><span class="comment"> *       - Moreover if M1 precedes M2 in the output, formally time stamps might be in the opposite order</span></div>
<div class="line"><a id="l00071" name="l00071"></a><span class="lineno">   71</span><span class="comment"> *         (even assuming, again, a well behaved clock).  (Informally, given how this is implemented internally,</span></div>
<div class="line"><a id="l00072" name="l00072"></a><span class="lineno">   72</span><span class="comment"> *         this is unlikely to be observed in practice, barring a wide absolute discrepancy between</span></div>
<div class="line"><a id="l00073" name="l00073"></a><span class="lineno">   73</span><span class="comment"> *         how long it takes to evaluate `ARG_stream_fragment` in M1 vs. M2.)</span></div>
<div class="line"><a id="l00074" name="l00074"></a><span class="lineno">   74</span><span class="comment"> *</span></div>
<div class="line"><a id="l00075" name="l00075"></a><span class="lineno">   75</span><span class="comment"> * The time stamp is obtained as soon as practically possible within the body of this macro.  Hence it reflects the time</span></div>
<div class="line"><a id="l00076" name="l00076"></a><span class="lineno">   76</span><span class="comment"> * at the moment just after the pre-logging statement finished, just before the log call site executes.  *After* this</span></div>
<div class="line"><a id="l00077" name="l00077"></a><span class="lineno">   77</span><span class="comment"> * is when `ARG_stream_fragment` is evaluated -- assuming the filter check passes -- and only after that might the</span></div>
<div class="line"><a id="l00078" name="l00078"></a><span class="lineno">   78</span><span class="comment"> * final output get queued (or possibly synchronously output, depending on nature of `get_logger()`).  This is why it&#39;s</span></div>
<div class="line"><a id="l00079" name="l00079"></a><span class="lineno">   79</span><span class="comment"> * technically possible that (even in the absence of system time going backwards) 2 messages from 2 different threads</span></div>
<div class="line"><a id="l00080" name="l00080"></a><span class="lineno">   80</span><span class="comment"> * might appear in the final output with slightly out-of-order time stamps.  Informally, this is unlikely, because</span></div>
<div class="line"><a id="l00081" name="l00081"></a><span class="lineno">   81</span><span class="comment"> * the `ARG_stream_fragment` evaluation would be on the order of a bunch of instructions that would complete in less</span></div>
<div class="line"><a id="l00082" name="l00082"></a><span class="lineno">   82</span><span class="comment"> * time than the microsecond resolution of time stamp output, in most cases, or maybe a handful of microseconds.</span></div>
<div class="line"><a id="l00083" name="l00083"></a><span class="lineno">   83</span><span class="comment"> * Anecdotally, I (ygoldfel) don&#39;t recall one instance of seeing this (out-of-order time stamps due to the</span></div>
<div class="line"><a id="l00084" name="l00084"></a><span class="lineno">   84</span><span class="comment"> * concurrency race implied by the above mechanism).</span></div>
<div class="line"><a id="l00085" name="l00085"></a><span class="lineno">   85</span><span class="comment"> * Nevertheless I mention it here for completeness, as well as to explain how it works.</span></div>
<div class="line"><a id="l00086" name="l00086"></a><span class="lineno">   86</span><span class="comment"> *</span></div>
<div class="line"><a id="l00087" name="l00087"></a><span class="lineno">   87</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00088" name="l00088"></a><span class="lineno">   88</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00089" name="l00089"></a><span class="lineno">   89</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00090" name="l00090"></a><span class="lineno">   90</span><span class="comment"> *</span></div>
<div class="line"><a id="l00091" name="l00091"></a><span class="lineno">   91</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00092" name="l00092"></a><span class="lineno">   92</span><span class="comment"> *        Same as in FLOW_LOG_WITHOUT_CHECKING().</span></div>
<div class="line"><a id="l00093" name="l00093"></a><span class="lineno">   93</span><span class="comment"> *</span></div>
<div class="line"><a id="l00094" name="l00094"></a><span class="lineno">   94</span><span class="comment"> * @todo We can avoid using macros for this and similar APIs by requiring the user to use commas instead of the usual</span></div>
<div class="line"><a id="l00095" name="l00095"></a><span class="lineno">   95</span><span class="comment"> * `&lt;&lt;` and by implementing this as a variadic function template (C++11 feature).</span></div>
<div class="line"><a id="l00096" name="l00096"></a><span class="lineno">   96</span><span class="comment"> *</span></div>
<div class="line"><a id="l00097" name="l00097"></a><span class="lineno">   97</span><span class="comment"> * Thus, while it&#39;d be no longer possible to write</span></div>
<div class="line"><a id="l00098" name="l00098"></a><span class="lineno">   98</span><span class="comment"> *</span></div>
<div class="line"><a id="l00099" name="l00099"></a><span class="lineno">   99</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00100" name="l00100"></a><span class="lineno">  100</span><span class="comment"> *   FLOW_LOG_WARNING(&quot;Result: [&quot; &lt;&lt; std::setfill(&#39;0&#39;) &lt;&lt; num &lt;&lt; &quot;].&quot;);</span></div>
<div class="line"><a id="l00101" name="l00101"></a><span class="lineno">  101</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00102" name="l00102"></a><span class="lineno">  102</span><span class="comment"> *</span></div>
<div class="line"><a id="l00103" name="l00103"></a><span class="lineno">  103</span><span class="comment"> * one would instead write</span></div>
<div class="line"><a id="l00104" name="l00104"></a><span class="lineno">  104</span><span class="comment"> *</span></div>
<div class="line"><a id="l00105" name="l00105"></a><span class="lineno">  105</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00106" name="l00106"></a><span class="lineno">  106</span><span class="comment"> *   flow::log::warning(&quot;Result: [&quot;, std::setfill(&#39;0&#39;), num, &quot;].&quot;);</span></div>
<div class="line"><a id="l00107" name="l00107"></a><span class="lineno">  107</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00108" name="l00108"></a><span class="lineno">  108</span><span class="comment"> *</span></div>
<div class="line"><a id="l00109" name="l00109"></a><span class="lineno">  109</span><span class="comment"> * which is fairly close and still reasonably readable.  However, one would need to be mindful of</span></div>
<div class="line"><a id="l00110" name="l00110"></a><span class="lineno">  110</span><span class="comment"> * performance; hopefully the optimizer would still inline everything</span></div>
<div class="line"><a id="l00111" name="l00111"></a><span class="lineno">  111</span><span class="comment"> * instead of adding a number of function calls compared to this macro implementation whose side benefit is</span></div>
<div class="line"><a id="l00112" name="l00112"></a><span class="lineno">  112</span><span class="comment"> * guaranteed inlining.  Generally, though, macros are bad and should be eliminated where possible; just don&#39;t mess</span></div>
<div class="line"><a id="l00113" name="l00113"></a><span class="lineno">  113</span><span class="comment"> * up speed in something as common as logging.  In addition, if it&#39;s NOT inlined, the number of functions generated</span></div>
<div class="line"><a id="l00114" name="l00114"></a><span class="lineno">  114</span><span class="comment"> * by the template&#39;s many instantiations would be rather large, though I suppose that&#39;s not necessarily *worse* than</span></div>
<div class="line"><a id="l00115" name="l00115"></a><span class="lineno">  115</span><span class="comment"> * full-on inlining thereof -- just *different*.  (Still, consider how many different configurations would pop up</span></div>
<div class="line"><a id="l00116" name="l00116"></a><span class="lineno">  116</span><span class="comment"> * as a result of all the different log messages!)  Also keep in mind that *fully* inlining all of this would require</span></div>
<div class="line"><a id="l00117" name="l00117"></a><span class="lineno">  117</span><span class="comment"> * the build engine to be capable of link-time optimization (FLTO), and the build script to enable FLTO.</span></div>
<div class="line"><a id="l00118" name="l00118"></a><span class="lineno">  118</span><span class="comment"> * *Unfortunately* it would be impossible for the non-macro to refer to a `get_logger()`</span></div>
<div class="line"><a id="l00119" name="l00119"></a><span class="lineno">  119</span><span class="comment"> * in the call&#39;s context, so it would be necessary for this to be passed in as an argument,</span></div>
<div class="line"><a id="l00120" name="l00120"></a><span class="lineno">  120</span><span class="comment"> * significantly lowering the ease of use of the API.  That said, flow::log::Logger itself could simply</span></div>
<div class="line"><a id="l00121" name="l00121"></a><span class="lineno">  121</span><span class="comment"> * implement all these APIs as class methods instead of their being free functions.</span></div>
<div class="line"><a id="l00122" name="l00122"></a><span class="lineno">  122</span><span class="comment"> * Then one could even (when desired) write such things as</span></div>
<div class="line"><a id="l00123" name="l00123"></a><span class="lineno">  123</span><span class="comment"> *</span></div>
<div class="line"><a id="l00124" name="l00124"></a><span class="lineno">  124</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00125" name="l00125"></a><span class="lineno">  125</span><span class="comment"> *   Logger some_logger(...); // Some Logger that is not available through get_logger() as would be more typical.</span></div>
<div class="line"><a id="l00126" name="l00126"></a><span class="lineno">  126</span><span class="comment"> *   some_logger.warning(&quot;Error detected: [&quot;, err_num, &quot;].&quot;);</span></div>
<div class="line"><a id="l00127" name="l00127"></a><span class="lineno">  127</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00128" name="l00128"></a><span class="lineno">  128</span><span class="comment"> *</span></div>
<div class="line"><a id="l00129" name="l00129"></a><span class="lineno">  129</span><span class="comment"> * and therefore FLOW_LOG_SET_CONTEXT() (another &quot;tricky&quot; macro) could be eliminated due to lack of necessity.</span></div>
<div class="line"><a id="l00130" name="l00130"></a><span class="lineno">  130</span><span class="comment"> * Finally, flow::log::Log_context (in the current design, to be derived from by all logging classes) would be used</span></div>
<div class="line"><a id="l00131" name="l00131"></a><span class="lineno">  131</span><span class="comment"> * like this:</span></div>
<div class="line"><a id="l00132" name="l00132"></a><span class="lineno">  132</span><span class="comment"> *</span></div>
<div class="line"><a id="l00133" name="l00133"></a><span class="lineno">  133</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00134" name="l00134"></a><span class="lineno">  134</span><span class="comment"> *   get_logger()-&gt;warning(&quot;Error detected: [&quot;, err_num, &quot;].&quot;);</span></div>
<div class="line"><a id="l00135" name="l00135"></a><span class="lineno">  135</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00136" name="l00136"></a><span class="lineno">  136</span><span class="comment"> *</span></div>
<div class="line"><a id="l00137" name="l00137"></a><span class="lineno">  137</span><span class="comment"> * It might also be advisable, for code brevity in such commonly referenced APIs, to add trivial forwarding methods</span></div>
<div class="line"><a id="l00138" name="l00138"></a><span class="lineno">  138</span><span class="comment"> * to flow::log::Log_context.  This is slightly questionable, as it&#39;s quite a bit of boiler-plate (needed every time one</span></div>
<div class="line"><a id="l00139" name="l00139"></a><span class="lineno">  139</span><span class="comment"> * might change this overall API) just to remove a few characters from each log call.  The above call would become:</span></div>
<div class="line"><a id="l00140" name="l00140"></a><span class="lineno">  140</span><span class="comment"> *</span></div>
<div class="line"><a id="l00141" name="l00141"></a><span class="lineno">  141</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00142" name="l00142"></a><span class="lineno">  142</span><span class="comment"> *   log_warning(&quot;Error detected: [&quot;, err_num, &quot;].&quot;); // Invoke superclass Log_context&#39;s Logger::warning() method.</span></div>
<div class="line"><a id="l00143" name="l00143"></a><span class="lineno">  143</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00144" name="l00144"></a><span class="lineno">  144</span><span class="comment"> *</span></div>
<div class="line"><a id="l00145" name="l00145"></a><span class="lineno">  145</span><span class="comment"> * which is a little more compact.  That can also be accomplished by having flow::log::Log_context implement</span></div>
<div class="line"><a id="l00146" name="l00146"></a><span class="lineno">  146</span><span class="comment"> * flow::log::Logger itself.  As a last note, `__LINE__` (etc.) can only be made useful via a macro, so one would still</span></div>
<div class="line"><a id="l00147" name="l00147"></a><span class="lineno">  147</span><span class="comment"> * be required to wrap around any API suggested above in a simple macro -- but this would be far superior (in this</span></div>
<div class="line"><a id="l00148" name="l00148"></a><span class="lineno">  148</span><span class="comment"> * particular dimension of avoiding macro insanity) to the level of macro-ness required at the moment.  All in all,</span></div>
<div class="line"><a id="l00149" name="l00149"></a><span class="lineno">  149</span><span class="comment"> * while I do hate macros, the present design seems reasonably strong, so the above rejiggering ideas don&#39;t feel</span></div>
<div class="line"><a id="l00150" name="l00150"></a><span class="lineno">  150</span><span class="comment"> * like no-brainers.</span></div>
<div class="line"><a id="l00151" name="l00151"></a><span class="lineno">  151</span><span class="comment"> */</span></div>
<div class="line"><a id="l00152" name="l00152"></a><span class="lineno"><a class="line" href="log_8hpp.html#a626c7dc4d3b4dc0b32a8aac8624d66bc">  152</a></span><span class="preprocessor">#define FLOW_LOG_WARNING(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00153" name="l00153"></a><span class="lineno">  153</span><span class="preprocessor">  FLOW_LOG_WITH_CHECKING(::flow::log::Sev::S_WARNING, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00154" name="l00154"></a><span class="lineno">  154</span><span class="comment"></span> </div>
<div class="line"><a id="l00155" name="l00155"></a><span class="lineno">  155</span><span class="comment">/**</span></div>
<div class="line"><a id="l00156" name="l00156"></a><span class="lineno">  156</span><span class="comment"> * Logs a FATAL message into flow::log::Logger `*get_logger()` with</span></div>
<div class="line"><a id="l00157" name="l00157"></a><span class="lineno">  157</span><span class="comment"> * flow::log::Component `get_log_component()`, if such logging</span></div>
<div class="line"><a id="l00158" name="l00158"></a><span class="lineno">  158</span><span class="comment"> * is enabled by the flow::log::Logger.  Analogous to FLOW_LOG_WARNING() but for the flow::log::Sev::S_FATAL severity.</span></div>
<div class="line"><a id="l00159" name="l00159"></a><span class="lineno">  159</span><span class="comment"> *</span></div>
<div class="line"><a id="l00160" name="l00160"></a><span class="lineno">  160</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00161" name="l00161"></a><span class="lineno">  161</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00162" name="l00162"></a><span class="lineno">  162</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00163" name="l00163"></a><span class="lineno">  163</span><span class="comment"> *</span></div>
<div class="line"><a id="l00164" name="l00164"></a><span class="lineno">  164</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00165" name="l00165"></a><span class="lineno">  165</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00166" name="l00166"></a><span class="lineno">  166</span><span class="comment"> */</span></div>
<div class="line"><a id="l00167" name="l00167"></a><span class="lineno"><a class="line" href="log_8hpp.html#a86c9eda3c93618933d751b675bdbefa5">  167</a></span><span class="preprocessor">#define FLOW_LOG_FATAL(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00168" name="l00168"></a><span class="lineno">  168</span><span class="preprocessor">  FLOW_LOG_WITH_CHECKING(::flow::log::Sev::S_FATAL, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00169" name="l00169"></a><span class="lineno">  169</span><span class="comment"></span> </div>
<div class="line"><a id="l00170" name="l00170"></a><span class="lineno">  170</span><span class="comment">/**</span></div>
<div class="line"><a id="l00171" name="l00171"></a><span class="lineno">  171</span><span class="comment"> * Logs an ERROR message into flow::log::Logger `*get_logger()` with</span></div>
<div class="line"><a id="l00172" name="l00172"></a><span class="lineno">  172</span><span class="comment"> * flow::log::Component `get_log_component()`, if such logging</span></div>
<div class="line"><a id="l00173" name="l00173"></a><span class="lineno">  173</span><span class="comment"> * is enabled by the flow::log::Logger.  Analogous to FLOW_LOG_WARNING() but for the flow::log::Sev::S_ERROR severity.</span></div>
<div class="line"><a id="l00174" name="l00174"></a><span class="lineno">  174</span><span class="comment"> *</span></div>
<div class="line"><a id="l00175" name="l00175"></a><span class="lineno">  175</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00176" name="l00176"></a><span class="lineno">  176</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00177" name="l00177"></a><span class="lineno">  177</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00178" name="l00178"></a><span class="lineno">  178</span><span class="comment"> *</span></div>
<div class="line"><a id="l00179" name="l00179"></a><span class="lineno">  179</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00180" name="l00180"></a><span class="lineno">  180</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00181" name="l00181"></a><span class="lineno">  181</span><span class="comment"> */</span></div>
<div class="line"><a id="l00182" name="l00182"></a><span class="lineno"><a class="line" href="log_8hpp.html#a9c1538676a14220c9a04f3480751eb54">  182</a></span><span class="preprocessor">#define FLOW_LOG_ERROR(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00183" name="l00183"></a><span class="lineno">  183</span><span class="preprocessor">  FLOW_LOG_WITH_CHECKING(::flow::log::Sev::S_ERROR, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00184" name="l00184"></a><span class="lineno">  184</span><span class="comment"></span> </div>
<div class="line"><a id="l00185" name="l00185"></a><span class="lineno">  185</span><span class="comment">/**</span></div>
<div class="line"><a id="l00186" name="l00186"></a><span class="lineno">  186</span><span class="comment"> * Logs an INFO message into flow::log::Logger `*get_logger()` with</span></div>
<div class="line"><a id="l00187" name="l00187"></a><span class="lineno">  187</span><span class="comment"> * flow::log::Component `get_log_component()`, if such logging</span></div>
<div class="line"><a id="l00188" name="l00188"></a><span class="lineno">  188</span><span class="comment"> * is enabled by the flow::log::Logger.  Analogous to FLOW_LOG_WARNING() but for the flow::log::Sev::S_INFO severity.</span></div>
<div class="line"><a id="l00189" name="l00189"></a><span class="lineno">  189</span><span class="comment"> *</span></div>
<div class="line"><a id="l00190" name="l00190"></a><span class="lineno">  190</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00191" name="l00191"></a><span class="lineno">  191</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00192" name="l00192"></a><span class="lineno">  192</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00193" name="l00193"></a><span class="lineno">  193</span><span class="comment"> *</span></div>
<div class="line"><a id="l00194" name="l00194"></a><span class="lineno">  194</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00195" name="l00195"></a><span class="lineno">  195</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00196" name="l00196"></a><span class="lineno">  196</span><span class="comment"> */</span></div>
<div class="line"><a id="l00197" name="l00197"></a><span class="lineno"><a class="line" href="log_8hpp.html#a325fdd4b5cf0be49b37d3b7b7c29070d">  197</a></span><span class="preprocessor">#define FLOW_LOG_INFO(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00198" name="l00198"></a><span class="lineno">  198</span><span class="preprocessor">  FLOW_LOG_WITH_CHECKING(::flow::log::Sev::S_INFO, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00199" name="l00199"></a><span class="lineno">  199</span><span class="comment"></span> </div>
<div class="line"><a id="l00200" name="l00200"></a><span class="lineno">  200</span><span class="comment">/**</span></div>
<div class="line"><a id="l00201" name="l00201"></a><span class="lineno">  201</span><span class="comment"> * Logs a DEBUG message into flow::log::Logger `*get_logger()` with</span></div>
<div class="line"><a id="l00202" name="l00202"></a><span class="lineno">  202</span><span class="comment"> * flow::log::Component `get_log_component()`, if such logging</span></div>
<div class="line"><a id="l00203" name="l00203"></a><span class="lineno">  203</span><span class="comment"> * is enabled by the flow::log::Logger.  Analogous to FLOW_LOG_WARNING() but for the flow::log::Sev::S_DEBUG severity.</span></div>
<div class="line"><a id="l00204" name="l00204"></a><span class="lineno">  204</span><span class="comment"> *</span></div>
<div class="line"><a id="l00205" name="l00205"></a><span class="lineno">  205</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00206" name="l00206"></a><span class="lineno">  206</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00207" name="l00207"></a><span class="lineno">  207</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00208" name="l00208"></a><span class="lineno">  208</span><span class="comment"> *</span></div>
<div class="line"><a id="l00209" name="l00209"></a><span class="lineno">  209</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00210" name="l00210"></a><span class="lineno">  210</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00211" name="l00211"></a><span class="lineno">  211</span><span class="comment"> */</span></div>
<div class="line"><a id="l00212" name="l00212"></a><span class="lineno"><a class="line" href="log_8hpp.html#a89710ddaee7323e168aa3587b66c6f90">  212</a></span><span class="preprocessor">#define FLOW_LOG_DEBUG(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00213" name="l00213"></a><span class="lineno">  213</span><span class="preprocessor">  FLOW_LOG_WITH_CHECKING(::flow::log::Sev::S_DEBUG, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00214" name="l00214"></a><span class="lineno">  214</span><span class="comment"></span> </div>
<div class="line"><a id="l00215" name="l00215"></a><span class="lineno">  215</span><span class="comment">/**</span></div>
<div class="line"><a id="l00216" name="l00216"></a><span class="lineno">  216</span><span class="comment"> * Logs a TRACE message into flow::log::Logger `*get_logger()` with</span></div>
<div class="line"><a id="l00217" name="l00217"></a><span class="lineno">  217</span><span class="comment"> * flow::log::Component `get_log_component()`, if such logging</span></div>
<div class="line"><a id="l00218" name="l00218"></a><span class="lineno">  218</span><span class="comment"> * is enabled by the flow::log::Logger.  Analogous to FLOW_LOG_WARNING() but for the flow::log::Sev::S_TRACE severity.</span></div>
<div class="line"><a id="l00219" name="l00219"></a><span class="lineno">  219</span><span class="comment"> *</span></div>
<div class="line"><a id="l00220" name="l00220"></a><span class="lineno">  220</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00221" name="l00221"></a><span class="lineno">  221</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00222" name="l00222"></a><span class="lineno">  222</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00223" name="l00223"></a><span class="lineno">  223</span><span class="comment"> *</span></div>
<div class="line"><a id="l00224" name="l00224"></a><span class="lineno">  224</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00225" name="l00225"></a><span class="lineno">  225</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00226" name="l00226"></a><span class="lineno">  226</span><span class="comment"> */</span></div>
<div class="line"><a id="l00227" name="l00227"></a><span class="lineno"><a class="line" href="log_8hpp.html#affcf2e4c496ce3f42adf981669c623b8">  227</a></span><span class="preprocessor">#define FLOW_LOG_TRACE(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00228" name="l00228"></a><span class="lineno">  228</span><span class="preprocessor">  FLOW_LOG_WITH_CHECKING(::flow::log::Sev::S_TRACE, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00229" name="l00229"></a><span class="lineno">  229</span><span class="comment"></span> </div>
<div class="line"><a id="l00230" name="l00230"></a><span class="lineno">  230</span><span class="comment">/**</span></div>
<div class="line"><a id="l00231" name="l00231"></a><span class="lineno">  231</span><span class="comment"> * Logs a DATA message into flow::log::Logger `*get_logger()` with</span></div>
<div class="line"><a id="l00232" name="l00232"></a><span class="lineno">  232</span><span class="comment"> * flow::log::Component `get_log_component()`, if such logging</span></div>
<div class="line"><a id="l00233" name="l00233"></a><span class="lineno">  233</span><span class="comment"> * is enabled by the flow::log::Logger.  Analogous to FLOW_LOG_WARNING() but for the flow::log::Sev::S_DATA severity.</span></div>
<div class="line"><a id="l00234" name="l00234"></a><span class="lineno">  234</span><span class="comment"> *</span></div>
<div class="line"><a id="l00235" name="l00235"></a><span class="lineno">  235</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00236" name="l00236"></a><span class="lineno">  236</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00237" name="l00237"></a><span class="lineno">  237</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00238" name="l00238"></a><span class="lineno">  238</span><span class="comment"> *</span></div>
<div class="line"><a id="l00239" name="l00239"></a><span class="lineno">  239</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00240" name="l00240"></a><span class="lineno">  240</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00241" name="l00241"></a><span class="lineno">  241</span><span class="comment"> */</span></div>
<div class="line"><a id="l00242" name="l00242"></a><span class="lineno"><a class="line" href="log_8hpp.html#a07561c1c3f16b6c2c7335a09e25298c9">  242</a></span><span class="preprocessor">#define FLOW_LOG_DATA(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00243" name="l00243"></a><span class="lineno">  243</span><span class="preprocessor">  FLOW_LOG_WITH_CHECKING(::flow::log::Sev::S_DATA, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00244" name="l00244"></a><span class="lineno">  244</span><span class="comment"></span> </div>
<div class="line"><a id="l00245" name="l00245"></a><span class="lineno">  245</span><span class="comment">/**</span></div>
<div class="line"><a id="l00246" name="l00246"></a><span class="lineno">  246</span><span class="comment"> * Logs a WARNING message into flow::log::Logger `*get_logger()` with</span></div>
<div class="line"><a id="l00247" name="l00247"></a><span class="lineno">  247</span><span class="comment"> * flow::log::Component `get_log_component()` regardless of</span></div>
<div class="line"><a id="l00248" name="l00248"></a><span class="lineno">  248</span><span class="comment"> * whether such logging is enabled by the flow::log::Logger.  Analogous to FLOW_LOG_WARNING() but without checking for</span></div>
<div class="line"><a id="l00249" name="l00249"></a><span class="lineno">  249</span><span class="comment"> * whether it is enabled (you should do so yourself; see the following note on this topic).</span></div>
<div class="line"><a id="l00250" name="l00250"></a><span class="lineno">  250</span><span class="comment"> *</span></div>
<div class="line"><a id="l00251" name="l00251"></a><span class="lineno">  251</span><span class="comment"> * @note If `get_logger()` is null, this is a no-op.  In practice, though,</span></div>
<div class="line"><a id="l00252" name="l00252"></a><span class="lineno">  252</span><span class="comment"> *       this case should have been eliminated as part of heeding the following warning:</span></div>
<div class="line"><a id="l00253" name="l00253"></a><span class="lineno">  253</span><span class="comment"> *</span></div>
<div class="line"><a id="l00254" name="l00254"></a><span class="lineno">  254</span><span class="comment"> * @warning If invoking this directly, API user must manually ensure the severity is enabled in the logger.</span></div>
<div class="line"><a id="l00255" name="l00255"></a><span class="lineno">  255</span><span class="comment"> *          Not doing so breaks (unenforced but nevertheless mandatory) rules of logging system.</span></div>
<div class="line"><a id="l00256" name="l00256"></a><span class="lineno">  256</span><span class="comment"> *</span></div>
<div class="line"><a id="l00257" name="l00257"></a><span class="lineno">  257</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00258" name="l00258"></a><span class="lineno">  258</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00259" name="l00259"></a><span class="lineno">  259</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00260" name="l00260"></a><span class="lineno">  260</span><span class="comment"> *</span></div>
<div class="line"><a id="l00261" name="l00261"></a><span class="lineno">  261</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00262" name="l00262"></a><span class="lineno">  262</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00263" name="l00263"></a><span class="lineno">  263</span><span class="comment"> */</span></div>
<div class="line"><a id="l00264" name="l00264"></a><span class="lineno"><a class="line" href="log_8hpp.html#a1bd954e4451fd00d23dec6b85ef15774">  264</a></span><span class="preprocessor">#define FLOW_LOG_WARNING_WITHOUT_CHECKING(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00265" name="l00265"></a><span class="lineno">  265</span><span class="preprocessor">  FLOW_LOG_WITHOUT_CHECKING(::flow::log::Sev::S_WARNING, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00266" name="l00266"></a><span class="lineno">  266</span><span class="comment"></span> </div>
<div class="line"><a id="l00267" name="l00267"></a><span class="lineno">  267</span><span class="comment">/**</span></div>
<div class="line"><a id="l00268" name="l00268"></a><span class="lineno">  268</span><span class="comment"> * Logs a FATAL message into flow::log::Logger `*get_logger()`</span></div>
<div class="line"><a id="l00269" name="l00269"></a><span class="lineno">  269</span><span class="comment"> * with flow::log::Component `get_log_component()` regardless of</span></div>
<div class="line"><a id="l00270" name="l00270"></a><span class="lineno">  270</span><span class="comment"> * whether such logging is enabled by the flow::log::Logger.  Analogous to FLOW_LOG_WARNING_WITHOUT_CHECKING()</span></div>
<div class="line"><a id="l00271" name="l00271"></a><span class="lineno">  271</span><span class="comment"> * but for the flow::log::Sev::S_FATAL severity.</span></div>
<div class="line"><a id="l00272" name="l00272"></a><span class="lineno">  272</span><span class="comment"> *</span></div>
<div class="line"><a id="l00273" name="l00273"></a><span class="lineno">  273</span><span class="comment"> * @note Same warnings and notes as for FLOW_LOG_WARNING_WITHOUT_CHECKING().</span></div>
<div class="line"><a id="l00274" name="l00274"></a><span class="lineno">  274</span><span class="comment"> *</span></div>
<div class="line"><a id="l00275" name="l00275"></a><span class="lineno">  275</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00276" name="l00276"></a><span class="lineno">  276</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00277" name="l00277"></a><span class="lineno">  277</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00278" name="l00278"></a><span class="lineno">  278</span><span class="comment"> *</span></div>
<div class="line"><a id="l00279" name="l00279"></a><span class="lineno">  279</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00280" name="l00280"></a><span class="lineno">  280</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00281" name="l00281"></a><span class="lineno">  281</span><span class="comment"> */</span></div>
<div class="line"><a id="l00282" name="l00282"></a><span class="lineno"><a class="line" href="log_8hpp.html#a5f2f44cddf64eadacb704e6cc592a635">  282</a></span><span class="preprocessor">#define FLOW_LOG_FATAL_WITHOUT_CHECKING(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00283" name="l00283"></a><span class="lineno">  283</span><span class="preprocessor">  FLOW_LOG_WITHOUT_CHECKING(::flow::log::Sev::S_FATAL, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00284" name="l00284"></a><span class="lineno">  284</span><span class="comment"></span> </div>
<div class="line"><a id="l00285" name="l00285"></a><span class="lineno">  285</span><span class="comment">/**</span></div>
<div class="line"><a id="l00286" name="l00286"></a><span class="lineno">  286</span><span class="comment"> * Logs an ERROR message into flow::log::Logger `*get_logger()`</span></div>
<div class="line"><a id="l00287" name="l00287"></a><span class="lineno">  287</span><span class="comment"> * with flow::log::Component `get_log_component()` regardless of</span></div>
<div class="line"><a id="l00288" name="l00288"></a><span class="lineno">  288</span><span class="comment"> * whether such logging is enabled by the flow::log::Logger.  Analogous to FLOW_LOG_WARNING_WITHOUT_CHECKING()</span></div>
<div class="line"><a id="l00289" name="l00289"></a><span class="lineno">  289</span><span class="comment"> * but for the flow::log::Sev::S_ERROR severity.</span></div>
<div class="line"><a id="l00290" name="l00290"></a><span class="lineno">  290</span><span class="comment"> *</span></div>
<div class="line"><a id="l00291" name="l00291"></a><span class="lineno">  291</span><span class="comment"> * @note Same warnings and notes as for FLOW_LOG_WARNING_WITHOUT_CHECKING().</span></div>
<div class="line"><a id="l00292" name="l00292"></a><span class="lineno">  292</span><span class="comment"> *</span></div>
<div class="line"><a id="l00293" name="l00293"></a><span class="lineno">  293</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00294" name="l00294"></a><span class="lineno">  294</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00295" name="l00295"></a><span class="lineno">  295</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00296" name="l00296"></a><span class="lineno">  296</span><span class="comment"> *</span></div>
<div class="line"><a id="l00297" name="l00297"></a><span class="lineno">  297</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00298" name="l00298"></a><span class="lineno">  298</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00299" name="l00299"></a><span class="lineno">  299</span><span class="comment"> */</span></div>
<div class="line"><a id="l00300" name="l00300"></a><span class="lineno"><a class="line" href="log_8hpp.html#a68153bafb54dcce136b9394738402133">  300</a></span><span class="preprocessor">#define FLOW_LOG_ERROR_WITHOUT_CHECKING(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00301" name="l00301"></a><span class="lineno">  301</span><span class="preprocessor">  FLOW_LOG_WITHOUT_CHECKING(::flow::log::Sev::S_ERROR, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00302" name="l00302"></a><span class="lineno">  302</span><span class="comment"></span> </div>
<div class="line"><a id="l00303" name="l00303"></a><span class="lineno">  303</span><span class="comment">/**</span></div>
<div class="line"><a id="l00304" name="l00304"></a><span class="lineno">  304</span><span class="comment"> * Logs an INFO message into flow::log::Logger `*get_logger()`</span></div>
<div class="line"><a id="l00305" name="l00305"></a><span class="lineno">  305</span><span class="comment"> * with flow::log::Component `get_log_component()` regardless of</span></div>
<div class="line"><a id="l00306" name="l00306"></a><span class="lineno">  306</span><span class="comment"> * whether such logging is enabled by the flow::log::Logger.  Analogous to FLOW_LOG_WARNING_WITHOUT_CHECKING()</span></div>
<div class="line"><a id="l00307" name="l00307"></a><span class="lineno">  307</span><span class="comment"> * but for the flow::log::Sev::S_INFO severity.</span></div>
<div class="line"><a id="l00308" name="l00308"></a><span class="lineno">  308</span><span class="comment"> *</span></div>
<div class="line"><a id="l00309" name="l00309"></a><span class="lineno">  309</span><span class="comment"> * @note Same warnings and notes as for FLOW_LOG_WARNING_WITHOUT_CHECKING().</span></div>
<div class="line"><a id="l00310" name="l00310"></a><span class="lineno">  310</span><span class="comment"> *</span></div>
<div class="line"><a id="l00311" name="l00311"></a><span class="lineno">  311</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00312" name="l00312"></a><span class="lineno">  312</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00313" name="l00313"></a><span class="lineno">  313</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00314" name="l00314"></a><span class="lineno">  314</span><span class="comment"> *</span></div>
<div class="line"><a id="l00315" name="l00315"></a><span class="lineno">  315</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00316" name="l00316"></a><span class="lineno">  316</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00317" name="l00317"></a><span class="lineno">  317</span><span class="comment"> */</span></div>
<div class="line"><a id="l00318" name="l00318"></a><span class="lineno"><a class="line" href="log_8hpp.html#a1be182a498bd3703311820fec76d04ff">  318</a></span><span class="preprocessor">#define FLOW_LOG_INFO_WITHOUT_CHECKING(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00319" name="l00319"></a><span class="lineno">  319</span><span class="preprocessor">  FLOW_LOG_WITHOUT_CHECKING(::flow::log::Sev::S_INFO, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00320" name="l00320"></a><span class="lineno">  320</span><span class="comment"></span> </div>
<div class="line"><a id="l00321" name="l00321"></a><span class="lineno">  321</span><span class="comment">/**</span></div>
<div class="line"><a id="l00322" name="l00322"></a><span class="lineno">  322</span><span class="comment"> * Logs a DEBUG message into flow::log::Logger `*get_logger()`</span></div>
<div class="line"><a id="l00323" name="l00323"></a><span class="lineno">  323</span><span class="comment"> * with flow::log::Component `get_log_component()` regardless of</span></div>
<div class="line"><a id="l00324" name="l00324"></a><span class="lineno">  324</span><span class="comment"> * whether such logging is enabled by the flow::log::Logger.  Analogous to FLOW_LOG_WARNING_WITHOUT_CHECKING()</span></div>
<div class="line"><a id="l00325" name="l00325"></a><span class="lineno">  325</span><span class="comment"> * but for the flow::log::Sev::S_DEBUG severity.</span></div>
<div class="line"><a id="l00326" name="l00326"></a><span class="lineno">  326</span><span class="comment"> *</span></div>
<div class="line"><a id="l00327" name="l00327"></a><span class="lineno">  327</span><span class="comment"> * @note Same warnings and notes as for FLOW_LOG_WARNING_WITHOUT_CHECKING().</span></div>
<div class="line"><a id="l00328" name="l00328"></a><span class="lineno">  328</span><span class="comment"> *</span></div>
<div class="line"><a id="l00329" name="l00329"></a><span class="lineno">  329</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00330" name="l00330"></a><span class="lineno">  330</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00331" name="l00331"></a><span class="lineno">  331</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00332" name="l00332"></a><span class="lineno">  332</span><span class="comment"> *</span></div>
<div class="line"><a id="l00333" name="l00333"></a><span class="lineno">  333</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00334" name="l00334"></a><span class="lineno">  334</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00335" name="l00335"></a><span class="lineno">  335</span><span class="comment"> */</span></div>
<div class="line"><a id="l00336" name="l00336"></a><span class="lineno"><a class="line" href="log_8hpp.html#ad3e7f5705279c17e1e22c2427c216d7c">  336</a></span><span class="preprocessor">#define FLOW_LOG_DEBUG_WITHOUT_CHECKING(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00337" name="l00337"></a><span class="lineno">  337</span><span class="preprocessor">  FLOW_LOG_WITHOUT_CHECKING(::flow::log::Sev::S_DEBUG, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00338" name="l00338"></a><span class="lineno">  338</span><span class="comment"></span> </div>
<div class="line"><a id="l00339" name="l00339"></a><span class="lineno">  339</span><span class="comment">/**</span></div>
<div class="line"><a id="l00340" name="l00340"></a><span class="lineno">  340</span><span class="comment"> * Logs a TRACE message into flow::log::Logger `*get_logger()`</span></div>
<div class="line"><a id="l00341" name="l00341"></a><span class="lineno">  341</span><span class="comment"> * with flow::log::Component `get_log_component()` regardless of</span></div>
<div class="line"><a id="l00342" name="l00342"></a><span class="lineno">  342</span><span class="comment"> * whether such logging is enabled by the flow::log::Logger.  Analogous to FLOW_LOG_WARNING_WITHOUT_CHECKING()</span></div>
<div class="line"><a id="l00343" name="l00343"></a><span class="lineno">  343</span><span class="comment"> * but for the flow::log::Sev::S_TRACE severity.</span></div>
<div class="line"><a id="l00344" name="l00344"></a><span class="lineno">  344</span><span class="comment"> *</span></div>
<div class="line"><a id="l00345" name="l00345"></a><span class="lineno">  345</span><span class="comment"> * @note Same warnings and notes as for FLOW_LOG_WARNING_WITHOUT_CHECKING().</span></div>
<div class="line"><a id="l00346" name="l00346"></a><span class="lineno">  346</span><span class="comment"> *</span></div>
<div class="line"><a id="l00347" name="l00347"></a><span class="lineno">  347</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00348" name="l00348"></a><span class="lineno">  348</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00349" name="l00349"></a><span class="lineno">  349</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00350" name="l00350"></a><span class="lineno">  350</span><span class="comment"> *</span></div>
<div class="line"><a id="l00351" name="l00351"></a><span class="lineno">  351</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00352" name="l00352"></a><span class="lineno">  352</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00353" name="l00353"></a><span class="lineno">  353</span><span class="comment"> */</span></div>
<div class="line"><a id="l00354" name="l00354"></a><span class="lineno"><a class="line" href="log_8hpp.html#a6b3b2cd7ddabf90a7c6ccd104a042cc6">  354</a></span><span class="preprocessor">#define FLOW_LOG_TRACE_WITHOUT_CHECKING(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00355" name="l00355"></a><span class="lineno">  355</span><span class="preprocessor">  FLOW_LOG_WITHOUT_CHECKING(::flow::log::Sev::S_TRACE, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00356" name="l00356"></a><span class="lineno">  356</span><span class="comment"></span> </div>
<div class="line"><a id="l00357" name="l00357"></a><span class="lineno">  357</span><span class="comment">/**</span></div>
<div class="line"><a id="l00358" name="l00358"></a><span class="lineno">  358</span><span class="comment"> * Logs a DATA message into flow::log::Logger `*get_logger()`</span></div>
<div class="line"><a id="l00359" name="l00359"></a><span class="lineno">  359</span><span class="comment"> * with flow::log::Component `get_log_component()` regardless of</span></div>
<div class="line"><a id="l00360" name="l00360"></a><span class="lineno">  360</span><span class="comment"> * whether such logging is enabled by the flow::log::Logger.  Analogous to</span></div>
<div class="line"><a id="l00361" name="l00361"></a><span class="lineno">  361</span><span class="comment"> * FLOW_LOG_WARNING_WITHOUT_CHECKING() but for the flow::log::Sev::S_DATA severity.</span></div>
<div class="line"><a id="l00362" name="l00362"></a><span class="lineno">  362</span><span class="comment"> *</span></div>
<div class="line"><a id="l00363" name="l00363"></a><span class="lineno">  363</span><span class="comment"> * @note Same warnings and notes as for FLOW_LOG_WARNING_WITHOUT_CHECKING().</span></div>
<div class="line"><a id="l00364" name="l00364"></a><span class="lineno">  364</span><span class="comment"> *</span></div>
<div class="line"><a id="l00365" name="l00365"></a><span class="lineno">  365</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00366" name="l00366"></a><span class="lineno">  366</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00367" name="l00367"></a><span class="lineno">  367</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00368" name="l00368"></a><span class="lineno">  368</span><span class="comment"> *</span></div>
<div class="line"><a id="l00369" name="l00369"></a><span class="lineno">  369</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00370" name="l00370"></a><span class="lineno">  370</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00371" name="l00371"></a><span class="lineno">  371</span><span class="comment"> */</span></div>
<div class="line"><a id="l00372" name="l00372"></a><span class="lineno"><a class="line" href="log_8hpp.html#a9aa1d91ba9eb26345d4b83588ac489cb">  372</a></span><span class="preprocessor">#define FLOW_LOG_DATA_WITHOUT_CHECKING(ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00373" name="l00373"></a><span class="lineno">  373</span><span class="preprocessor">  FLOW_LOG_WITHOUT_CHECKING(::flow::log::Sev::S_DATA, ARG_stream_fragment)</span></div>
<div class="line"><a id="l00374" name="l00374"></a><span class="lineno">  374</span><span class="comment"></span> </div>
<div class="line"><a id="l00375" name="l00375"></a><span class="lineno">  375</span><span class="comment">/**</span></div>
<div class="line"><a id="l00376" name="l00376"></a><span class="lineno">  376</span><span class="comment"> * For the rest of the block within which this macro is instantiated, causes all `FLOW_LOG_...()`</span></div>
<div class="line"><a id="l00377" name="l00377"></a><span class="lineno">  377</span><span class="comment"> * invocations to log to `ARG_logger_ptr` with component `flow::log::Component(ARG_component_payload)`, instead of the</span></div>
<div class="line"><a id="l00378" name="l00378"></a><span class="lineno">  378</span><span class="comment"> * normal `get_logger()` and `get_log_component()`, if there even such things are available in the block.  This is</span></div>
<div class="line"><a id="l00379" name="l00379"></a><span class="lineno">  379</span><span class="comment"> * useful, for example, in `static` methods, where there is no `get_logger()` or `get_log_component()` function defined,</span></div>
<div class="line"><a id="l00380" name="l00380"></a><span class="lineno">  380</span><span class="comment"> * but a flow::log::Logger and component payload are available (for example) via parameters.  It&#39;s also useful if one</span></div>
<div class="line"><a id="l00381" name="l00381"></a><span class="lineno">  381</span><span class="comment"> * wants to log to a different `Logger*` for some reason and/or (perhaps more likely) a different component.</span></div>
<div class="line"><a id="l00382" name="l00382"></a><span class="lineno">  382</span><span class="comment"> * Note that this creates or changes the meaning of the identifiers `get_logger` and `get_log_component` for the rest of</span></div>
<div class="line"><a id="l00383" name="l00383"></a><span class="lineno">  383</span><span class="comment"> * the block; in fact you may call `get_logger()` or `get_log_component()` directly for whatever nefarious purposes you</span></div>
<div class="line"><a id="l00384" name="l00384"></a><span class="lineno">  384</span><span class="comment"> * require, though it is suspected to be rare compared to just using `FLOW_LOG_...()` normally.</span></div>
<div class="line"><a id="l00385" name="l00385"></a><span class="lineno">  385</span><span class="comment"> *</span></div>
<div class="line"><a id="l00386" name="l00386"></a><span class="lineno">  386</span><span class="comment"> * Example:</span></div>
<div class="line"><a id="l00387" name="l00387"></a><span class="lineno">  387</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00388" name="l00388"></a><span class="lineno">  388</span><span class="comment"> *   // Suppose flow_node is a flow::Node object, which derives from Log_context.</span></div>
<div class="line"><a id="l00389" name="l00389"></a><span class="lineno">  389</span><span class="comment"> *   FLOW_LOG_SET_CONTEXT(flow_node.get_logger(), My_project_components::S_COOL_MODULE);</span></div>
<div class="line"><a id="l00390" name="l00390"></a><span class="lineno">  390</span><span class="comment"> *   // Logs with component S_COOL_MODULE to logger set above.</span></div>
<div class="line"><a id="l00391" name="l00391"></a><span class="lineno">  391</span><span class="comment"> *   FLOW_LOG_WARNING(&quot;Something horrible happened: [&quot; &lt;&lt; error_str &lt;&lt; &quot;].&quot;);</span></div>
<div class="line"><a id="l00392" name="l00392"></a><span class="lineno">  392</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00393" name="l00393"></a><span class="lineno">  393</span><span class="comment"> *</span></div>
<div class="line"><a id="l00394" name="l00394"></a><span class="lineno">  394</span><span class="comment"> * @note It will not compile if used 2+ times in the same block at the same nesting level.</span></div>
<div class="line"><a id="l00395" name="l00395"></a><span class="lineno">  395</span><span class="comment"> *       (The same applies to mixing with FLOW_LOG_SET_COMPONENT() or FLOW_LOG_SET_LOGGER().)</span></div>
<div class="line"><a id="l00396" name="l00396"></a><span class="lineno">  396</span><span class="comment"> *       However, one can create sub-blocks to work around this (likely very infrequent) situation.</span></div>
<div class="line"><a id="l00397" name="l00397"></a><span class="lineno">  397</span><span class="comment"> *</span></div>
<div class="line"><a id="l00398" name="l00398"></a><span class="lineno">  398</span><span class="comment"> * @param ARG_logger_ptr</span></div>
<div class="line"><a id="l00399" name="l00399"></a><span class="lineno">  399</span><span class="comment"> *        `ARG_logger_ptr` will be used as the `Logger*` in subsequent `FLOW_LOG_...()`</span></div>
<div class="line"><a id="l00400" name="l00400"></a><span class="lineno">  400</span><span class="comment"> *        invocations in this block.</span></div>
<div class="line"><a id="l00401" name="l00401"></a><span class="lineno">  401</span><span class="comment"> * @param ARG_component_payload</span></div>
<div class="line"><a id="l00402" name="l00402"></a><span class="lineno">  402</span><span class="comment"> *        `Component(ARG_component_payload)`, a light-weight holder of a copy of `ARG_component_payload`, will be used</span></div>
<div class="line"><a id="l00403" name="l00403"></a><span class="lineno">  403</span><span class="comment"> *        as the `const Component&amp;` in subsequent `FLOW_LOG_...()` invocations in this block.</span></div>
<div class="line"><a id="l00404" name="l00404"></a><span class="lineno">  404</span><span class="comment"> */</span></div>
<div class="line"><a id="l00405" name="l00405"></a><span class="lineno"><a class="line" href="log_8hpp.html#ae4b5d4fdd2eb052615620879dd74af95">  405</a></span><span class="preprocessor">#define FLOW_LOG_SET_CONTEXT(ARG_logger_ptr, ARG_component_payload) \</span></div>
<div class="line"><a id="l00406" name="l00406"></a><span class="lineno">  406</span><span class="preprocessor">  FLOW_LOG_SET_LOGGER(ARG_logger_ptr); \</span></div>
<div class="line"><a id="l00407" name="l00407"></a><span class="lineno">  407</span><span class="preprocessor">  FLOW_LOG_SET_COMPONENT(ARG_component_payload);</span></div>
<div class="line"><a id="l00408" name="l00408"></a><span class="lineno">  408</span><span class="comment"></span> </div>
<div class="line"><a id="l00409" name="l00409"></a><span class="lineno">  409</span><span class="comment">/**</span></div>
<div class="line"><a id="l00410" name="l00410"></a><span class="lineno">  410</span><span class="comment"> * Equivalent to FLOW_LOG_SET_CONTEXT() but sets the `get_logger` only.</span></div>
<div class="line"><a id="l00411" name="l00411"></a><span class="lineno">  411</span><span class="comment"> *</span></div>
<div class="line"><a id="l00412" name="l00412"></a><span class="lineno">  412</span><span class="comment"> * @param ARG_logger_ptr</span></div>
<div class="line"><a id="l00413" name="l00413"></a><span class="lineno">  413</span><span class="comment"> *        See FLOW_LOG_SET_CONTEXT().</span></div>
<div class="line"><a id="l00414" name="l00414"></a><span class="lineno">  414</span><span class="comment"> */</span></div>
<div class="line"><a id="l00415" name="l00415"></a><span class="lineno"><a class="line" href="log_8hpp.html#ad4958fbd8673f48be76bf8e5e11d0522">  415</a></span><span class="preprocessor">#define FLOW_LOG_SET_LOGGER(ARG_logger_ptr) \</span></div>
<div class="line"><a id="l00416" name="l00416"></a><span class="lineno">  416</span><span class="preprocessor">  [[maybe_unused]] \</span></div>
<div class="line"><a id="l00417" name="l00417"></a><span class="lineno">  417</span><span class="preprocessor">    const auto get_logger \</span></div>
<div class="line"><a id="l00418" name="l00418"></a><span class="lineno">  418</span><span class="preprocessor">      = [logger_ptr_copy = static_cast&lt;::flow::log::Logger*&gt;(ARG_logger_ptr)] \</span></div>
<div class="line"><a id="l00419" name="l00419"></a><span class="lineno">  419</span><span class="preprocessor">          () -&gt; ::flow::log::Logger* { return logger_ptr_copy; }</span></div>
<div class="line"><a id="l00420" name="l00420"></a><span class="lineno">  420</span><span class="comment"></span> </div>
<div class="line"><a id="l00421" name="l00421"></a><span class="lineno">  421</span><span class="comment">/**</span></div>
<div class="line"><a id="l00422" name="l00422"></a><span class="lineno">  422</span><span class="comment"> * Equivalent to FLOW_LOG_SET_CONTEXT() but sets the `get_log_component` only.</span></div>
<div class="line"><a id="l00423" name="l00423"></a><span class="lineno">  423</span><span class="comment"> *</span></div>
<div class="line"><a id="l00424" name="l00424"></a><span class="lineno">  424</span><span class="comment"> * @internal</span></div>
<div class="line"><a id="l00425" name="l00425"></a><span class="lineno">  425</span><span class="comment"> * ### Impl/perf discussion ###</span></div>
<div class="line"><a id="l00426" name="l00426"></a><span class="lineno">  426</span><span class="comment"> * If a free or `static` member function or lambda is frequently called, and it needs to log, it will make perf</span></div>
<div class="line"><a id="l00427" name="l00427"></a><span class="lineno">  427</span><span class="comment"> * aspects of this macro (and thus of FLOW_LOG_SET_CONTEXT()) significant to overall perf.  Hence let&#39;s unpack</span></div>
<div class="line"><a id="l00428" name="l00428"></a><span class="lineno">  428</span><span class="comment"> * what computation occurs.</span></div>
<div class="line"><a id="l00429" name="l00429"></a><span class="lineno">  429</span><span class="comment"> *   - When this macro (and thus FLOW_LOG_SET_CONTEXT()) is called (usually near the top of free/whatever function):</span></div>
<div class="line"><a id="l00430" name="l00430"></a><span class="lineno">  430</span><span class="comment"> *     It creates a lambda with one capture, a flow::log::Component, constructed via its 1-arg ctor form.</span></div>
<div class="line"><a id="l00431" name="l00431"></a><span class="lineno">  431</span><span class="comment"> *     That lambda object is, in fact, identical to a `struct` instance with a single `Component` member thus</span></div>
<div class="line"><a id="l00432" name="l00432"></a><span class="lineno">  432</span><span class="comment"> *     constructed.  As of this writing that constuctor: saves the pointer `&amp;(typeid(T))`, where `T` is the particular</span></div>
<div class="line"><a id="l00433" name="l00433"></a><span class="lineno">  433</span><span class="comment"> *     `enum class` type of `ARG_component_payload`; and saves the integer payload of the `enum` value</span></div>
<div class="line"><a id="l00434" name="l00434"></a><span class="lineno">  434</span><span class="comment"> *     `ARG_component_payload`.  A pointer and an integer are light-weight to copy, indeed.  Additionally, in practice,</span></div>
<div class="line"><a id="l00435" name="l00435"></a><span class="lineno">  435</span><span class="comment"> *     both values are probably known at compile time; hence the compiler might further inline the &quot;copy.&quot;</span></div>
<div class="line"><a id="l00436" name="l00436"></a><span class="lineno">  436</span><span class="comment"> *     Hence we conclude the copy operation is fast.</span></div>
<div class="line"><a id="l00437" name="l00437"></a><span class="lineno">  437</span><span class="comment"> *     - The quasi-`struct`&#39;s two members are stored directly on the stack.  There is no heap involved.  Hence we</span></div>
<div class="line"><a id="l00438" name="l00438"></a><span class="lineno">  438</span><span class="comment"> *       conclude there is no hidden cost in messing with the heap by either using a lambda or whatever is stored</span></div>
<div class="line"><a id="l00439" name="l00439"></a><span class="lineno">  439</span><span class="comment"> *       inside the lambda.</span></div>
<div class="line"><a id="l00440" name="l00440"></a><span class="lineno">  440</span><span class="comment"> *   - When `get_log_component()` is called (at every log call site in the free/whatever function, probably):</span></div>
<div class="line"><a id="l00441" name="l00441"></a><span class="lineno">  441</span><span class="comment"> *     It calls the aforementioned lambda&#39;s compiler-generated `operator()()`.  This just returns a pointer to the</span></div>
<div class="line"><a id="l00442" name="l00442"></a><span class="lineno">  442</span><span class="comment"> *     stack-stored `struct`.  Compilers tend to auto-inline (short) lambda `operator()()` calls, so there&#39;s probably</span></div>
<div class="line"><a id="l00443" name="l00443"></a><span class="lineno">  443</span><span class="comment"> *     not even the overhead of a function call.  Hence we conclude this is pretty fast.</span></div>
<div class="line"><a id="l00444" name="l00444"></a><span class="lineno">  444</span><span class="comment"> *</span></div>
<div class="line"><a id="l00445" name="l00445"></a><span class="lineno">  445</span><span class="comment"> * Looks fine perf-wise (at least in theory).</span></div>
<div class="line"><a id="l00446" name="l00446"></a><span class="lineno">  446</span><span class="comment"> * @endinternal</span></div>
<div class="line"><a id="l00447" name="l00447"></a><span class="lineno">  447</span><span class="comment"> *</span></div>
<div class="line"><a id="l00448" name="l00448"></a><span class="lineno">  448</span><span class="comment"> * @param ARG_component_payload</span></div>
<div class="line"><a id="l00449" name="l00449"></a><span class="lineno">  449</span><span class="comment"> *        See FLOW_LOG_SET_CONTEXT().</span></div>
<div class="line"><a id="l00450" name="l00450"></a><span class="lineno">  450</span><span class="comment"> */</span></div>
<div class="line"><a id="l00451" name="l00451"></a><span class="lineno"><a class="line" href="log_8hpp.html#a3105444b58d309b7aa9847ea045bd42d">  451</a></span><span class="preprocessor">#define FLOW_LOG_SET_COMPONENT(ARG_component_payload) \</span></div>
<div class="line"><a id="l00452" name="l00452"></a><span class="lineno">  452</span><span class="preprocessor">  [[maybe_unused]] \</span></div>
<div class="line"><a id="l00453" name="l00453"></a><span class="lineno">  453</span><span class="preprocessor">    const auto get_log_component = [component = ::flow::log::Component(ARG_component_payload)] \</span></div>
<div class="line"><a id="l00454" name="l00454"></a><span class="lineno">  454</span><span class="preprocessor">                                     () -&gt; const ::flow::log::Component &amp; \</span></div>
<div class="line"><a id="l00455" name="l00455"></a><span class="lineno">  455</span><span class="preprocessor">  { \</span></div>
<div class="line"><a id="l00456" name="l00456"></a><span class="lineno">  456</span><span class="preprocessor">    return component; \</span></div>
<div class="line"><a id="l00457" name="l00457"></a><span class="lineno">  457</span><span class="preprocessor">  }</span></div>
<div class="line"><a id="l00458" name="l00458"></a><span class="lineno">  458</span><span class="comment"></span> </div>
<div class="line"><a id="l00459" name="l00459"></a><span class="lineno">  459</span><span class="comment">/**</span></div>
<div class="line"><a id="l00460" name="l00460"></a><span class="lineno">  460</span><span class="comment"> * Logs a message of the specified severity into flow::log::Logger `*get_logger()` with flow::log::Component</span></div>
<div class="line"><a id="l00461" name="l00461"></a><span class="lineno">  461</span><span class="comment"> * `get_log_component()` if such logging is enabled by said flow::log::Logger.  The behavior is identical</span></div>
<div class="line"><a id="l00462" name="l00462"></a><span class="lineno">  462</span><span class="comment"> * to that by FLOW_LOG_WARNING() and similar, but one specifies the severity as an argument instead of it being</span></div>
<div class="line"><a id="l00463" name="l00463"></a><span class="lineno">  463</span><span class="comment"> * hard-coded into the macro name itself.</span></div>
<div class="line"><a id="l00464" name="l00464"></a><span class="lineno">  464</span><span class="comment"> *</span></div>
<div class="line"><a id="l00465" name="l00465"></a><span class="lineno">  465</span><span class="comment"> * @note It is important that ARG_stream_fragment is actually evaluated only if Logger::should_log() is</span></div>
<div class="line"><a id="l00466" name="l00466"></a><span class="lineno">  466</span><span class="comment"> *       true.  Otherwise resources are wasted on constructing a message string that never gets</span></div>
<div class="line"><a id="l00467" name="l00467"></a><span class="lineno">  467</span><span class="comment"> *       logged.  That&#39;s a (the?) reason Logger:should_log() and Logger::do_log() are mutually decoupled in</span></div>
<div class="line"><a id="l00468" name="l00468"></a><span class="lineno">  468</span><span class="comment"> *       that interface.</span></div>
<div class="line"><a id="l00469" name="l00469"></a><span class="lineno">  469</span><span class="comment"> *</span></div>
<div class="line"><a id="l00470" name="l00470"></a><span class="lineno">  470</span><span class="comment"> * @param ARG_sev</span></div>
<div class="line"><a id="l00471" name="l00471"></a><span class="lineno">  471</span><span class="comment"> *        Severity (type log::Sev).</span></div>
<div class="line"><a id="l00472" name="l00472"></a><span class="lineno">  472</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00473" name="l00473"></a><span class="lineno">  473</span><span class="comment"> *        Same as in FLOW_LOG_WARNING().</span></div>
<div class="line"><a id="l00474" name="l00474"></a><span class="lineno">  474</span><span class="comment"> *</span></div>
<div class="line"><a id="l00475" name="l00475"></a><span class="lineno">  475</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00476" name="l00476"></a><span class="lineno">  476</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00477" name="l00477"></a><span class="lineno">  477</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00478" name="l00478"></a><span class="lineno">  478</span><span class="comment"> *</span></div>
<div class="line"><a id="l00479" name="l00479"></a><span class="lineno">  479</span><span class="comment"> * @internal</span></div>
<div class="line"><a id="l00480" name="l00480"></a><span class="lineno">  480</span><span class="comment"> * @todo In FLOW_LOG_WITH_CHECKING(), save `get_logger()` and `get_log_component()` return values in such a way as to be</span></div>
<div class="line"><a id="l00481" name="l00481"></a><span class="lineno">  481</span><span class="comment"> * reused by the FLOW_LOG_WITHOUT_CHECKING() invoked by the former macro if `should_log() == true`.  As it stands, they</span></div>
<div class="line"><a id="l00482" name="l00482"></a><span class="lineno">  482</span><span class="comment"> * are called again inside the latter macro.  In the most-common case, wherein Log_context is used for those</span></div>
<div class="line"><a id="l00483" name="l00483"></a><span class="lineno">  483</span><span class="comment"> * two expressions, this should get inline-optimized to be maximally fast anyway.  With `FLOW_LOG_SET_*()`, though,</span></div>
<div class="line"><a id="l00484" name="l00484"></a><span class="lineno">  484</span><span class="comment"> * it might be a bit slower than that.  Technically, one can make their own `get_logger` and `get_log_component`</span></div>
<div class="line"><a id="l00485" name="l00485"></a><span class="lineno">  485</span><span class="comment"> * identifiers that might do something slower still -- though it&#39;s unlikely (and as of this writing unprecedented).</span></div>
<div class="line"><a id="l00486" name="l00486"></a><span class="lineno">  486</span><span class="comment"> * So I would not call this pressing, but on the other hand... just do it!  The implementation code will be somewhat</span></div>
<div class="line"><a id="l00487" name="l00487"></a><span class="lineno">  487</span><span class="comment"> * hairier though.</span></div>
<div class="line"><a id="l00488" name="l00488"></a><span class="lineno">  488</span><span class="comment"> */</span></div>
<div class="line"><a id="l00489" name="l00489"></a><span class="lineno"><a class="line" href="log_8hpp.html#a692bbadd8b5c3e9cef7a0bbea1915e66">  489</a></span><span class="preprocessor">#define FLOW_LOG_WITH_CHECKING(ARG_sev, ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00490" name="l00490"></a><span class="lineno">  490</span><span class="preprocessor">  FLOW_UTIL_SEMICOLON_SAFE \</span></div>
<div class="line"><a id="l00491" name="l00491"></a><span class="lineno">  491</span><span class="preprocessor">  ( \</span></div>
<div class="line"><a id="l00492" name="l00492"></a><span class="lineno">  492</span><span class="preprocessor">    ::flow::log::Logger const * const FLOW_LOG_W_CHK_logger = get_logger(); \</span></div>
<div class="line"><a id="l00493" name="l00493"></a><span class="lineno">  493</span><span class="preprocessor">    if (FLOW_LOG_W_CHK_logger &amp;&amp; FLOW_LOG_W_CHK_logger-&gt;should_log(ARG_sev, get_log_component())) \</span></div>
<div class="line"><a id="l00494" name="l00494"></a><span class="lineno">  494</span><span class="preprocessor">    { \</span></div>
<div class="line"><a id="l00495" name="l00495"></a><span class="lineno">  495</span><span class="preprocessor">      FLOW_LOG_WITHOUT_CHECKING(ARG_sev, ARG_stream_fragment); \</span></div>
<div class="line"><a id="l00496" name="l00496"></a><span class="lineno">  496</span><span class="preprocessor">    } \</span></div>
<div class="line"><a id="l00497" name="l00497"></a><span class="lineno">  497</span><span class="preprocessor">  )</span></div>
<div class="line"><a id="l00498" name="l00498"></a><span class="lineno">  498</span><span class="comment"></span> </div>
<div class="line"><a id="l00499" name="l00499"></a><span class="lineno">  499</span><span class="comment">/**</span></div>
<div class="line"><a id="l00500" name="l00500"></a><span class="lineno">  500</span><span class="comment"> * Identical to FLOW_LOG_WITH_CHECKING() but foregoes the filter (Logger::should_log()) check.  No-op if</span></div>
<div class="line"><a id="l00501" name="l00501"></a><span class="lineno">  501</span><span class="comment"> * `get_logger()` returns null.  Internally, all other log-call-site macros ultimately build on top of this one</span></div>
<div class="line"><a id="l00502" name="l00502"></a><span class="lineno">  502</span><span class="comment"> * except FLOW_LOG_DO_LOG().</span></div>
<div class="line"><a id="l00503" name="l00503"></a><span class="lineno">  503</span><span class="comment"> *</span></div>
<div class="line"><a id="l00504" name="l00504"></a><span class="lineno">  504</span><span class="comment"> * Context information obtained and possibly logged is file/function/line, thread nickname/ID, time stamp, etc.</span></div>
<div class="line"><a id="l00505" name="l00505"></a><span class="lineno">  505</span><span class="comment"> * The message is given as the `&lt;&lt;`-using `ostream` fragment</span></div>
<div class="line"><a id="l00506" name="l00506"></a><span class="lineno">  506</span><span class="comment"> * in `ARG_stream_fragment` argument.  Example (note the 2nd argument containing a stream output fragment):</span></div>
<div class="line"><a id="l00507" name="l00507"></a><span class="lineno">  507</span><span class="comment"> *</span></div>
<div class="line"><a id="l00508" name="l00508"></a><span class="lineno">  508</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00509" name="l00509"></a><span class="lineno">  509</span><span class="comment"> *   FLOW_LOG_WITHOUT_CHECKING(flow::log::Sev::S_WARNING,</span></div>
<div class="line"><a id="l00510" name="l00510"></a><span class="lineno">  510</span><span class="comment"> *                             &quot;Failed [&quot; &lt;&lt; n_times &lt;&lt; &quot;] times; bailing out!&quot;);</span></div>
<div class="line"><a id="l00511" name="l00511"></a><span class="lineno">  511</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00512" name="l00512"></a><span class="lineno">  512</span><span class="comment"> *</span></div>
<div class="line"><a id="l00513" name="l00513"></a><span class="lineno">  513</span><span class="comment"> * @note This macro is the lowest-level API that user should invoke to actually log, except FLOW_LOG_DO_LOG().</span></div>
<div class="line"><a id="l00514" name="l00514"></a><span class="lineno">  514</span><span class="comment"> *       Usually she&#39;d invoke something higher-level like FLOW_LOG_WARNING(), etc.; but at times more control</span></div>
<div class="line"><a id="l00515" name="l00515"></a><span class="lineno">  515</span><span class="comment"> *       is desirable for performance or other reasons -- but even then one should not call anything below this</span></div>
<div class="line"><a id="l00516" name="l00516"></a><span class="lineno">  516</span><span class="comment"> *       level without an extremely excellent reason.  See FLOW_LOG_DO_LOG() for discussion of the latter.</span></div>
<div class="line"><a id="l00517" name="l00517"></a><span class="lineno">  517</span><span class="comment"> *</span></div>
<div class="line"><a id="l00518" name="l00518"></a><span class="lineno">  518</span><span class="comment"> * @warning If invoking this directly, API user must manually ensure the severity is enabled in the `Logger`.</span></div>
<div class="line"><a id="l00519" name="l00519"></a><span class="lineno">  519</span><span class="comment"> *          Not doing so breaks (unenforced but nevertheless mandatory) rules of logging system.</span></div>
<div class="line"><a id="l00520" name="l00520"></a><span class="lineno">  520</span><span class="comment"> *</span></div>
<div class="line"><a id="l00521" name="l00521"></a><span class="lineno">  521</span><span class="comment"> * ### Severity selection ###</span></div>
<div class="line"><a id="l00522" name="l00522"></a><span class="lineno">  522</span><span class="comment"> * Before selecting a severity for your log call site, please consider the discussion in the flow::log::Sev</span></div>
<div class="line"><a id="l00523" name="l00523"></a><span class="lineno">  523</span><span class="comment"> * doc header.</span></div>
<div class="line"><a id="l00524" name="l00524"></a><span class="lineno">  524</span><span class="comment"> *</span></div>
<div class="line"><a id="l00525" name="l00525"></a><span class="lineno">  525</span><span class="comment"> * @param ARG_sev</span></div>
<div class="line"><a id="l00526" name="l00526"></a><span class="lineno">  526</span><span class="comment"> *        Severity (type flow::log::Sev).</span></div>
<div class="line"><a id="l00527" name="l00527"></a><span class="lineno">  527</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00528" name="l00528"></a><span class="lineno">  528</span><span class="comment"> *        Fragment of code as if writing to a standard `ostream`.</span></div>
<div class="line"><a id="l00529" name="l00529"></a><span class="lineno">  529</span><span class="comment"> *        A terminating newline will be auto-appended to this eventually and therefore should generally not</span></div>
<div class="line"><a id="l00530" name="l00530"></a><span class="lineno">  530</span><span class="comment"> *        be included by the invoker.  (Such a terminating newline would manifest as a blank line, likely.)</span></div>
<div class="line"><a id="l00531" name="l00531"></a><span class="lineno">  531</span><span class="comment"> */</span></div>
<div class="line"><a id="l00532" name="l00532"></a><span class="lineno"><a class="line" href="log_8hpp.html#a5daa2b6d16edea74bb8bddc75f7fb801">  532</a></span><span class="preprocessor">#define FLOW_LOG_WITHOUT_CHECKING(ARG_sev, ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00533" name="l00533"></a><span class="lineno">  533</span><span class="preprocessor">  FLOW_UTIL_SEMICOLON_SAFE \</span></div>
<div class="line"><a id="l00534" name="l00534"></a><span class="lineno">  534</span><span class="preprocessor">  ( \</span></div>
<div class="line"><a id="l00535" name="l00535"></a><span class="lineno">  535</span><span class="preprocessor">    using ::flow::util::Thread_id; \</span></div>
<div class="line"><a id="l00536" name="l00536"></a><span class="lineno">  536</span><span class="preprocessor">    using ::flow::log::Logger; \</span></div>
<div class="line"><a id="l00537" name="l00537"></a><span class="lineno">  537</span><span class="preprocessor">    using ::flow::log::Component; \</span></div>
<div class="line"><a id="l00538" name="l00538"></a><span class="lineno">  538</span><span class="preprocessor">    using ::flow::util::String_view; \</span></div>
<div class="line"><a id="l00539" name="l00539"></a><span class="lineno">  539</span><span class="preprocessor">    using ::flow::util::get_last_path_segment; \</span></div>
<div class="line"><a id="l00540" name="l00540"></a><span class="lineno">  540</span><span class="preprocessor">    using ::std::chrono::system_clock; \</span></div>
<div class="line"><a id="l00541" name="l00541"></a><span class="lineno">  541</span><span class="preprocessor">    using ::std::string; \</span></div>
<div class="line"><a id="l00542" name="l00542"></a><span class="lineno">  542</span><span class="preprocessor">    Logger* const FLOW_LOG_WO_CHK_logger = get_logger(); \</span></div>
<div class="line"><a id="l00543" name="l00543"></a><span class="lineno">  543</span><span class="preprocessor">    if (!FLOW_LOG_WO_CHK_logger) </span><span class="comment">/* Usually a preceding filter/should_log() check would&#39;ve eliminated this but.... */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00544" name="l00544"></a><span class="lineno">  544</span><span class="preprocessor">    { \</span></div>
<div class="line"><a id="l00545" name="l00545"></a><span class="lineno">  545</span><span class="preprocessor">      break; \</span></div>
<div class="line"><a id="l00546" name="l00546"></a><span class="lineno">  546</span><span class="preprocessor">    } \</span></div>
<div class="line"><a id="l00547" name="l00547"></a><span class="lineno">  547</span><span class="preprocessor">    </span><span class="comment">/* else */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00548" name="l00548"></a><span class="lineno">  548</span><span class="preprocessor">    </span><span class="comment">/* Important: This is from the time-of-day/calendar clock, which is not steady, monotonic, etc.; *but* it is */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00549" name="l00549"></a><span class="lineno">  549</span><span class="preprocessor">    </span><span class="comment">/* convertible to a UTC time with cosmic meaning to humands; that is invaluable. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00550" name="l00550"></a><span class="lineno">  550</span><span class="preprocessor">    auto const&amp; FLOW_LOG_WO_CHK_time_stamp = system_clock::now(); \</span></div>
<div class="line"><a id="l00551" name="l00551"></a><span class="lineno">  551</span><span class="preprocessor">    </span><span class="comment">/* See Msg_metadata::m_msg_src_file doc. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00552" name="l00552"></a><span class="lineno">  552</span><span class="preprocessor">    </span><span class="comment">/* @todo The __FILE/FUNCTION__ stuff was far more inlined, but gcc 5.4 hit an internal compiler error (bug)! */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00553" name="l00553"></a><span class="lineno">  553</span><span class="preprocessor">    </span><span class="comment">/* This verbose step-by-step way of doing it jiggled the bug away.  Put it back when bug goes away maybe. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00554" name="l00554"></a><span class="lineno">  554</span><span class="preprocessor">    </span><span class="comment">/* Note either way it&#39;s optimized to the same thing, since the following 7 expressions all have constant */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00555" name="l00555"></a><span class="lineno">  555</span><span class="preprocessor">    </span><span class="comment">/* values at compile time as desired in m_msg_src_file doc header; and even formally guaranteed via constexpr. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00556" name="l00556"></a><span class="lineno">  556</span><span class="preprocessor">    </span><span class="comment">/* Warning: Something about this is brittle, in that if one makes a false move the compiler bug comes back. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00557" name="l00557"></a><span class="lineno">  557</span><span class="preprocessor">    </span><span class="comment">/* That&#39;s even when doing it this multi-step way.  Leaving this comment in as moral support for maintainers. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00558" name="l00558"></a><span class="lineno">  558</span><span class="preprocessor">    constexpr char const * FLOW_LOG_WO_CHK_file_ptr = __FILE__; \</span></div>
<div class="line"><a id="l00559" name="l00559"></a><span class="lineno">  559</span><span class="preprocessor">    constexpr size_t FLOW_LOG_WO_CHK_file_sz = sizeof(__FILE__) - 1; \</span></div>
<div class="line"><a id="l00560" name="l00560"></a><span class="lineno">  560</span><span class="preprocessor">    constexpr char const * FLOW_LOG_WO_CHK_func_ptr = __FUNCTION__; \</span></div>
<div class="line"><a id="l00561" name="l00561"></a><span class="lineno">  561</span><span class="preprocessor">    constexpr size_t FLOW_LOG_WO_CHK_func_sz = sizeof(__FUNCTION__) - 1; \</span></div>
<div class="line"><a id="l00562" name="l00562"></a><span class="lineno">  562</span><span class="preprocessor">    constexpr String_view FLOW_LOG_WO_CHK_full_file_str(FLOW_LOG_WO_CHK_file_ptr, FLOW_LOG_WO_CHK_file_sz); \</span></div>
<div class="line"><a id="l00563" name="l00563"></a><span class="lineno">  563</span><span class="preprocessor">    </span><span class="comment">/* Yes -- get_last_path_segment() is constexpr and will thus &quot;execute&quot; at compile time! */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00564" name="l00564"></a><span class="lineno">  564</span><span class="preprocessor">    constexpr String_view FLOW_LOG_WO_CHK_file_str = get_last_path_segment(FLOW_LOG_WO_CHK_full_file_str); \</span></div>
<div class="line"><a id="l00565" name="l00565"></a><span class="lineno">  565</span><span class="preprocessor">    constexpr String_view FLOW_LOG_WO_CHK_func_str(FLOW_LOG_WO_CHK_func_ptr, FLOW_LOG_WO_CHK_func_sz); \</span></div>
<div class="line"><a id="l00566" name="l00566"></a><span class="lineno">  566</span><span class="preprocessor">    const Component&amp; FLOW_LOG_WO_CHK_component = get_log_component(); \</span></div>
<div class="line"><a id="l00567" name="l00567"></a><span class="lineno">  567</span><span class="preprocessor">    string FLOW_LOG_WO_CHK_call_thread_nickname; \</span></div>
<div class="line"><a id="l00568" name="l00568"></a><span class="lineno">  568</span><span class="preprocessor">    Thread_id FLOW_LOG_WO_CHK_call_thread_id; \</span></div>
<div class="line"><a id="l00569" name="l00569"></a><span class="lineno">  569</span><span class="preprocessor">    Logger::set_thread_info(&amp;FLOW_LOG_WO_CHK_call_thread_nickname, &amp;FLOW_LOG_WO_CHK_call_thread_id); \</span></div>
<div class="line"><a id="l00570" name="l00570"></a><span class="lineno">  570</span><span class="preprocessor">    FLOW_LOG_DO_LOG(FLOW_LOG_WO_CHK_logger, FLOW_LOG_WO_CHK_component, ARG_sev, FLOW_LOG_WO_CHK_file_str, __LINE__, \</span></div>
<div class="line"><a id="l00571" name="l00571"></a><span class="lineno">  571</span><span class="preprocessor">                    FLOW_LOG_WO_CHK_func_str, FLOW_LOG_WO_CHK_time_stamp, FLOW_LOG_WO_CHK_call_thread_nickname, \</span></div>
<div class="line"><a id="l00572" name="l00572"></a><span class="lineno">  572</span><span class="preprocessor">                    FLOW_LOG_WO_CHK_call_thread_id, ARG_stream_fragment); \</span></div>
<div class="line"><a id="l00573" name="l00573"></a><span class="lineno">  573</span><span class="preprocessor">    </span><span class="comment">/* FLOW_LOG_WO_CHK_call_thread_nickname is now hosed. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00574" name="l00574"></a><span class="lineno">  574</span><span class="preprocessor">  ) </span><span class="comment">/* FLOW_UTIL_SEMICOLON_SAFE() */</span><span class="preprocessor"></span></div>
<div class="line"><a id="l00575" name="l00575"></a><span class="lineno">  575</span><span class="comment"></span> </div>
<div class="line"><a id="l00576" name="l00576"></a><span class="lineno">  576</span><span class="comment">/**</span></div>
<div class="line"><a id="l00577" name="l00577"></a><span class="lineno">  577</span><span class="comment"> * Lowest-level logging API accessible to the user, this is identical to FLOW_LOG_WITHOUT_CHECKING() but expects all</span></div>
<div class="line"><a id="l00578" name="l00578"></a><span class="lineno">  578</span><span class="comment"> * pieces of metadata in addition to the message and log::Sev, plus the flow::log::Logger, to be supplied as macro</span></div>
<div class="line"><a id="l00579" name="l00579"></a><span class="lineno">  579</span><span class="comment"> * arguments.</span></div>
<div class="line"><a id="l00580" name="l00580"></a><span class="lineno">  580</span><span class="comment"> *</span></div>
<div class="line"><a id="l00581" name="l00581"></a><span class="lineno">  581</span><span class="comment"> * Internally, all other log-call-site macros ultimately build on top of this one.</span></div>
<div class="line"><a id="l00582" name="l00582"></a><span class="lineno">  582</span><span class="comment"> *</span></div>
<div class="line"><a id="l00583" name="l00583"></a><span class="lineno">  583</span><span class="comment"> * @note From public user&#39;s point of view: It&#39;s flow::log::Logger::should_log() that allows the message argument to be</span></div>
<div class="line"><a id="l00584" name="l00584"></a><span class="lineno">  584</span><span class="comment"> *       built using `ostream&lt;&lt;` semantics instead of having to instantiate an intermediate flow::util::String_ostream</span></div>
<div class="line"><a id="l00585" name="l00585"></a><span class="lineno">  585</span><span class="comment"> *       (which has performance overhead and is more verbose).  Why not just use a higher-level macro -- at least</span></div>
<div class="line"><a id="l00586" name="l00586"></a><span class="lineno">  586</span><span class="comment"> *       as high-level as FLOW_LOG_WITHOUT_CHECKING() -- instead?  Answer: In some cases there is a source of metadata,</span></div>
<div class="line"><a id="l00587" name="l00587"></a><span class="lineno">  587</span><span class="comment"> *       like file and line number, that comes from a different source than (e.g.) `__FILE__` and `__LINE__` at the log</span></div>
<div class="line"><a id="l00588" name="l00588"></a><span class="lineno">  588</span><span class="comment"> *       call site; e.g., when logging from another log API through flow::log.</span></div>
<div class="line"><a id="l00589" name="l00589"></a><span class="lineno">  589</span><span class="comment"> *</span></div>
<div class="line"><a id="l00590" name="l00590"></a><span class="lineno">  590</span><span class="comment"> * @warning If invoking this directly, API user must manually ensure the severity/component is enabled in the `Logger`.</span></div>
<div class="line"><a id="l00591" name="l00591"></a><span class="lineno">  591</span><span class="comment"> *          Not doing so breaks (unenforced but nevertheless mandatory) rules of logging system.</span></div>
<div class="line"><a id="l00592" name="l00592"></a><span class="lineno">  592</span><span class="comment"> * @warning If invoking this directly, API user must manually ensure `ARG_logger_ptr` is not null.  Otherwise behavior</span></div>
<div class="line"><a id="l00593" name="l00593"></a><span class="lineno">  593</span><span class="comment"> *          is undefined.</span></div>
<div class="line"><a id="l00594" name="l00594"></a><span class="lineno">  594</span><span class="comment"> *</span></div>
<div class="line"><a id="l00595" name="l00595"></a><span class="lineno">  595</span><span class="comment"> * @param ARG_logger_ptr</span></div>
<div class="line"><a id="l00596" name="l00596"></a><span class="lineno">  596</span><span class="comment"> *        A `Logger*` through which to log; not null.</span></div>
<div class="line"><a id="l00597" name="l00597"></a><span class="lineno">  597</span><span class="comment"> * @param ARG_component</span></div>
<div class="line"><a id="l00598" name="l00598"></a><span class="lineno">  598</span><span class="comment"> *        See Msg_metadata (reference copied into it).</span></div>
<div class="line"><a id="l00599" name="l00599"></a><span class="lineno">  599</span><span class="comment"> * @param ARG_sev</span></div>
<div class="line"><a id="l00600" name="l00600"></a><span class="lineno">  600</span><span class="comment"> *        See Msg_metadata (`enum` value copied into it).</span></div>
<div class="line"><a id="l00601" name="l00601"></a><span class="lineno">  601</span><span class="comment"> * @param ARG_file_view</span></div>
<div class="line"><a id="l00602" name="l00602"></a><span class="lineno">  602</span><span class="comment"> *        See Msg_metadata (`String_view` copied into it).  Reminder: Underlying memory may need to remain valid</span></div>
<div class="line"><a id="l00603" name="l00603"></a><span class="lineno">  603</span><span class="comment"> *        asynchronously (read: indefinitely); usually it&#39;s a literal in static storage.</span></div>
<div class="line"><a id="l00604" name="l00604"></a><span class="lineno">  604</span><span class="comment"> * @param ARG_line</span></div>
<div class="line"><a id="l00605" name="l00605"></a><span class="lineno">  605</span><span class="comment"> *        See Msg_metadata (integer copied into it).</span></div>
<div class="line"><a id="l00606" name="l00606"></a><span class="lineno">  606</span><span class="comment"> * @param ARG_func_view</span></div>
<div class="line"><a id="l00607" name="l00607"></a><span class="lineno">  607</span><span class="comment"> *        See Msg_metadata (`String_view` copied into it).  Reminder: Same as for `ARG_file_view`.</span></div>
<div class="line"><a id="l00608" name="l00608"></a><span class="lineno">  608</span><span class="comment"> * @param ARG_time_stamp</span></div>
<div class="line"><a id="l00609" name="l00609"></a><span class="lineno">  609</span><span class="comment"> *        See Msg_metadata (scalar copied into it).</span></div>
<div class="line"><a id="l00610" name="l00610"></a><span class="lineno">  610</span><span class="comment"> * @param ARG_call_thread_nickname_str_moved</span></div>
<div class="line"><a id="l00611" name="l00611"></a><span class="lineno">  611</span><span class="comment"> *        See Msg_metadata (this `std::string` is *moved* into it and thus made empty).</span></div>
<div class="line"><a id="l00612" name="l00612"></a><span class="lineno">  612</span><span class="comment"> * @param ARG_call_thread_id</span></div>
<div class="line"><a id="l00613" name="l00613"></a><span class="lineno">  613</span><span class="comment"> *        See Msg_metadata (scalar copied into it).</span></div>
<div class="line"><a id="l00614" name="l00614"></a><span class="lineno">  614</span><span class="comment"> * @param ARG_stream_fragment</span></div>
<div class="line"><a id="l00615" name="l00615"></a><span class="lineno">  615</span><span class="comment"> *        See FLOW_LOG_WITHOUT_CHECKING().</span></div>
<div class="line"><a id="l00616" name="l00616"></a><span class="lineno">  616</span><span class="comment"> *</span></div>
<div class="line"><a id="l00617" name="l00617"></a><span class="lineno">  617</span><span class="comment"> * @internal</span></div>
<div class="line"><a id="l00618" name="l00618"></a><span class="lineno">  618</span><span class="comment"> *</span></div>
<div class="line"><a id="l00619" name="l00619"></a><span class="lineno">  619</span><span class="comment"> * ### Implementation discussion ###</span></div>
<div class="line"><a id="l00620" name="l00620"></a><span class="lineno">  620</span><span class="comment"> *</span></div>
<div class="line"><a id="l00621" name="l00621"></a><span class="lineno">  621</span><span class="comment"> * The implementation here must be as performant as humanly possible.  Every single logged message (albeit</span></div>
<div class="line"><a id="l00622" name="l00622"></a><span class="lineno">  622</span><span class="comment"> * only assuming severity [or any other filter] checks have passed, meaning a message is IN FACT logged) will</span></div>
<div class="line"><a id="l00623" name="l00623"></a><span class="lineno">  623</span><span class="comment"> * execute this code.</span></div>
<div class="line"><a id="l00624" name="l00624"></a><span class="lineno">  624</span><span class="comment"> *</span></div>
<div class="line"><a id="l00625" name="l00625"></a><span class="lineno">  625</span><span class="comment"> * In this implementation, one keeps reusing a thread-local `string`, cleared each time this is invoked and then</span></div>
<div class="line"><a id="l00626" name="l00626"></a><span class="lineno">  626</span><span class="comment"> * written to.  (The clearing doesn&#39;t deallocate anything; it only updates an internal length integer to 0!)</span></div>
<div class="line"><a id="l00627" name="l00627"></a><span class="lineno">  627</span><span class="comment"> * If Logger::logs_asynchronously() is `false`, then the Logger synchronously outputs the message and has no need</span></div>
<div class="line"><a id="l00628" name="l00628"></a><span class="lineno">  628</span><span class="comment"> * to make some intemediate copy of either the message or the metadata (time stamp, etc.).  However, if</span></div>
<div class="line"><a id="l00629" name="l00629"></a><span class="lineno">  629</span><span class="comment"> * it is `true` (as for heavy-duty logger Async_file_logger), then Logger must make a copy of the aforementioned</span></div>
<div class="line"><a id="l00630" name="l00630"></a><span class="lineno">  630</span><span class="comment"> * thread-local message string, so that it can be asynchronously logged later (probably by some other worker thread</span></div>
<div class="line"><a id="l00631" name="l00631"></a><span class="lineno">  631</span><span class="comment"> * used by the Logger), and deallocated.  This implementation allows for both work-flows; also see below to-do.</span></div>
<div class="line"><a id="l00632" name="l00632"></a><span class="lineno">  632</span><span class="comment"> *</span></div>
<div class="line"><a id="l00633" name="l00633"></a><span class="lineno">  633</span><span class="comment"> * @todo An alternative copy-free implementation of the asynchronous FLOW_LOG_DO_LOG() work-flow</span></div>
<div class="line"><a id="l00634" name="l00634"></a><span class="lineno">  634</span><span class="comment"> * is possible.  The basic idea of using a thread-local non-reallocating work string is just fine in the</span></div>
<div class="line"><a id="l00635" name="l00635"></a><span class="lineno">  635</span><span class="comment"> * non-`logs_asynchronously()` (i.e., synchronous) Logger flow.  In the asynchronous flow, however, it involves</span></div>
<div class="line"><a id="l00636" name="l00636"></a><span class="lineno">  636</span><span class="comment"> * an added message copy.  Instead -- as done in certain major server software author is familiar with -- one</span></div>
<div class="line"><a id="l00637" name="l00637"></a><span class="lineno">  637</span><span class="comment"> * could (perhaps in the async flow only) allocate a new string in each FLOW_LOG_DO_LOG() (in rare cases</span></div>
<div class="line"><a id="l00638" name="l00638"></a><span class="lineno">  638</span><span class="comment"> * reallocating, even repeatedly, if more space is needed); then pass that pointer around, until it is asynchronously</span></div>
<div class="line"><a id="l00639" name="l00639"></a><span class="lineno">  639</span><span class="comment"> * written out by Logger impl; then deallocate it.  Thus, a copy is eliminated in the async workflow.  A complicating</span></div>
<div class="line"><a id="l00640" name="l00640"></a><span class="lineno">  640</span><span class="comment"> * factor is that the current system maintains a format state across separate log call sites in a given thread; this</span></div>
<div class="line"><a id="l00641" name="l00641"></a><span class="lineno">  641</span><span class="comment"> * change would (if naively implemented at least) eliminate that feature -- but this could be considered acceptable.</span></div>
<div class="line"><a id="l00642" name="l00642"></a><span class="lineno">  642</span><span class="comment"> * (Still, do realize that, for example, in today&#39;s feature set one can set the `chrono` I/O formatting to show short</span></div>
<div class="line"><a id="l00643" name="l00643"></a><span class="lineno">  643</span><span class="comment"> * unit names like `2ms` instead of `2 milliseconds`; and one need do it only once; but with this change one would</span></div>
<div class="line"><a id="l00644" name="l00644"></a><span class="lineno">  644</span><span class="comment"> * need to do it in every log call site.  That would be, I can attest, rather annoying.  Additionally, make sure the</span></div>
<div class="line"><a id="l00645" name="l00645"></a><span class="lineno">  645</span><span class="comment"> * behavior is consistent in the sync and async work-flows.)  A related wrinkle is that if we add special support for</span></div>
<div class="line"><a id="l00646" name="l00646"></a><span class="lineno">  646</span><span class="comment"> * `printf()`-style log call sites (a to-do in flow::log doc header as of this writing), then in that case since</span></div>
<div class="line"><a id="l00647" name="l00647"></a><span class="lineno">  647</span><span class="comment"> * there is no expectation of such format statefulness in the first place, in that flow that particular concern isn&#39;t</span></div>
<div class="line"><a id="l00648" name="l00648"></a><span class="lineno">  648</span><span class="comment"> * a concern.  (Sub-to-do: If one did this, an extra-optimized further idea is to avoid the repeated allocs/deallocs</span></div>
<div class="line"><a id="l00649" name="l00649"></a><span class="lineno">  649</span><span class="comment"> * by maintaining a pool of already-allocated buffers to be reused opportunistically.)  Bottom line: I claim the</span></div>
<div class="line"><a id="l00650" name="l00650"></a><span class="lineno">  650</span><span class="comment"> * existing thing is pretty good; the extra copy is IMO unlikely to affect real performance, because (1) it&#39;s only</span></div>
<div class="line"><a id="l00651" name="l00651"></a><span class="lineno">  651</span><span class="comment"> * one copy in the context of quite a bit of similar copying and other ops going on while writing out the string; and</span></div>
<div class="line"><a id="l00652" name="l00652"></a><span class="lineno">  652</span><span class="comment"> * (2) if the message is so verbose as to affect performance *at all*, then it will probably affect it regardless of</span></div>
<div class="line"><a id="l00653" name="l00653"></a><span class="lineno">  653</span><span class="comment"> * the extra copy (in other words, its verbosity must be increased, or the filter verbosity must be decreased --</span></div>
<div class="line"><a id="l00654" name="l00654"></a><span class="lineno">  654</span><span class="comment"> * avoiding this exta internal copy feels in my [ygoldfel] personal opinion like rearranging deck chairs on the</span></div>
<div class="line"><a id="l00655" name="l00655"></a><span class="lineno">  655</span><span class="comment"> * Titanic).  So, this to-do should probably be to-done at some point, but it doesn&#39;t feel urgent.  And since there are</span></div>
<div class="line"><a id="l00656" name="l00656"></a><span class="lineno">  656</span><span class="comment"> * quite a few subtleties involved, as shown above, it&#39;s natural to resist doing it until truly necessary.</span></div>
<div class="line"><a id="l00657" name="l00657"></a><span class="lineno">  657</span><span class="comment"> *</span></div>
<div class="line"><a id="l00658" name="l00658"></a><span class="lineno">  658</span><span class="comment"> * @todo Time stamp subtlety: It might not be crazy to log not just the time stamp of entry to this macro but also</span></div>
<div class="line"><a id="l00659" name="l00659"></a><span class="lineno">  659</span><span class="comment"> * some indication how long it took to evaluate the rest and finally output it to the ultimate device/whatever.</span></div>
<div class="line"><a id="l00660" name="l00660"></a><span class="lineno">  660</span><span class="comment"> * It could be an optional differential or something, like &quot;timestamp+diff,&quot; with diff in microseconds or something.</span></div>
<div class="line"><a id="l00661" name="l00661"></a><span class="lineno">  661</span><span class="comment"> *</span></div>
<div class="line"><a id="l00662" name="l00662"></a><span class="lineno">  662</span><span class="comment"> * @todo Time stamp source: The current implementation uses the system clock to generate time stamps (a/k/a POSIX time),</span></div>
<div class="line"><a id="l00663" name="l00663"></a><span class="lineno">  663</span><span class="comment"> * but consider optionally or mandatorily using the high-resolution clock instead (or additionally?).</span></div>
<div class="line"><a id="l00664" name="l00664"></a><span class="lineno">  664</span><span class="comment"> * This has pros and cons; all or most time stamps elsewhere use the system clock also, so this allows for easy</span></div>
<div class="line"><a id="l00665" name="l00665"></a><span class="lineno">  665</span><span class="comment"> * cross-referencing against other systems and logs.  There&#39;s also the question of how to express an absolute time,</span></div>
<div class="line"><a id="l00666" name="l00666"></a><span class="lineno">  666</span><span class="comment"> * as usually the high-resolution clock starts at system startup -- not as humanly useful as a &quot;calendar&quot; (UTC) time,</span></div>
<div class="line"><a id="l00667" name="l00667"></a><span class="lineno">  667</span><span class="comment"> * which -- while useful humanly -- is *not* steady/monotonic/etc.  There is no reasonable conversion between</span></div>
<div class="line"><a id="l00668" name="l00668"></a><span class="lineno">  668</span><span class="comment"> * `Fine_clock::now()` and a calendar time (boost.chrono docs say this unequivocally which is a confirmation).</span></div>
<div class="line"><a id="l00669" name="l00669"></a><span class="lineno">  669</span><span class="comment"> * The pros include: (1) higher precision and resolution; (2) that time always flows forward and at a uniform rate</span></div>
<div class="line"><a id="l00670" name="l00670"></a><span class="lineno">  670</span><span class="comment"> * without possibility of time going back or forward due to human/otherwise clock sets or rare events like daylight</span></div>
<div class="line"><a id="l00671" name="l00671"></a><span class="lineno">  671</span><span class="comment"> * savings and leap seconds; or (3) to summarize, something more suited as a quick-and-dirty way to measure how long</span></div>
<div class="line"><a id="l00672" name="l00672"></a><span class="lineno">  672</span><span class="comment"> * things take in the program, like an always-on, log-integrated version of perf::Checkpointing_timer.</span></div>
<div class="line"><a id="l00673" name="l00673"></a><span class="lineno">  673</span><span class="comment"> * As of this writing all out-of-the-box log::Logger implementations and log::Config allow the output of human-readable</span></div>
<div class="line"><a id="l00674" name="l00674"></a><span class="lineno">  674</span><span class="comment"> * as well as sec.usec-from-Epoch time stamps.  One approach might be to replace the latter *only* with the high-rez</span></div>
<div class="line"><a id="l00675" name="l00675"></a><span class="lineno">  675</span><span class="comment"> * clock&#39;s time stamps, perhaps optionally, while leaving the human-readable one alone.  Note: There is an important</span></div>
<div class="line"><a id="l00676" name="l00676"></a><span class="lineno">  676</span><span class="comment"> * test to perform here, which is the time cost of obtaining either time stamp.  E.g., the high-rez time stamp might</span></div>
<div class="line"><a id="l00677" name="l00677"></a><span class="lineno">  677</span><span class="comment"> * be much slower -- or maybe the opposite!  To test this, (1) add the POSIX-time clock into the perf::Clock_type</span></div>
<div class="line"><a id="l00678" name="l00678"></a><span class="lineno">  678</span><span class="comment"> * `enum`, with all associated (fairly straightforward) changes in `flow::perf`; and (2) test the perf characteristics</span></div>
<div class="line"><a id="l00679" name="l00679"></a><span class="lineno">  679</span><span class="comment"> * of this new clock.  Certain code exists outside of Flow itself that already automatically tests all `Clock_type`s,</span></div>
<div class="line"><a id="l00680" name="l00680"></a><span class="lineno">  680</span><span class="comment"> * so it would quickly give the answer.  (Secondary to-do: Be less vague about where this program resides, in this</span></div>
<div class="line"><a id="l00681" name="l00681"></a><span class="lineno">  681</span><span class="comment"> * comment.  I, ygoldfel, have the answer at any rate and am only omitting it here for boring process reasons.)</span></div>
<div class="line"><a id="l00682" name="l00682"></a><span class="lineno">  682</span><span class="comment"> */</span></div>
<div class="line"><a id="l00683" name="l00683"></a><span class="lineno"><a class="line" href="log_8hpp.html#ab07c4bca2d59872736d0d9717b05aeb1">  683</a></span><span class="preprocessor">#define FLOW_LOG_DO_LOG(ARG_logger_ptr, \</span></div>
<div class="line"><a id="l00684" name="l00684"></a><span class="lineno">  684</span><span class="preprocessor">                        ARG_component, ARG_sev, ARG_file_view, ARG_line, ARG_func_view, \</span></div>
<div class="line"><a id="l00685" name="l00685"></a><span class="lineno">  685</span><span class="preprocessor">                        ARG_time_stamp, ARG_call_thread_nickname_str_moved, \</span></div>
<div class="line"><a id="l00686" name="l00686"></a><span class="lineno">  686</span><span class="preprocessor">                        ARG_call_thread_id, ARG_stream_fragment) \</span></div>
<div class="line"><a id="l00687" name="l00687"></a><span class="lineno">  687</span><span class="preprocessor">  FLOW_UTIL_SEMICOLON_SAFE \</span></div>
<div class="line"><a id="l00688" name="l00688"></a><span class="lineno">  688</span><span class="preprocessor">  ( \</span></div>
<div class="line"><a id="l00689" name="l00689"></a><span class="lineno">  689</span><span class="preprocessor">    using ::flow::log::Thread_local_string_appender; \</span></div>
<div class="line"><a id="l00690" name="l00690"></a><span class="lineno">  690</span><span class="preprocessor">    using ::flow::log::this_thread_sync_msg_metadata_ptr; \</span></div>
<div class="line"><a id="l00691" name="l00691"></a><span class="lineno">  691</span><span class="preprocessor">    using ::flow::log::Logger; \</span></div>
<div class="line"><a id="l00692" name="l00692"></a><span class="lineno">  692</span><span class="preprocessor">    using ::flow::log::Msg_metadata; \</span></div>
<div class="line"><a id="l00693" name="l00693"></a><span class="lineno">  693</span><span class="preprocessor">    using ::flow::util::String_view; \</span></div>
<div class="line"><a id="l00694" name="l00694"></a><span class="lineno">  694</span><span class="preprocessor">    using ::std::flush; \</span></div>
<div class="line"><a id="l00695" name="l00695"></a><span class="lineno">  695</span><span class="preprocessor">    Logger* const FLOW_LOG_DO_LOG_logger = ARG_logger_ptr; </span><span class="comment">/* Note: As advertised, it must NOT be null. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00696" name="l00696"></a><span class="lineno">  696</span><span class="preprocessor">    </span><span class="comment">/* If first use this thread/logger combo, create necessary structures for writing stream fragment to a string. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00697" name="l00697"></a><span class="lineno">  697</span><span class="preprocessor">    </span><span class="comment">/* If subsequent use with that combo, reuse already created structures to save cycles. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00698" name="l00698"></a><span class="lineno">  698</span><span class="preprocessor">    </span><span class="comment">/* We could&#39;ve just created string { locally } and used util::ostream_op_to_string(), which would */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00699" name="l00699"></a><span class="lineno">  699</span><span class="preprocessor">    </span><span class="comment">/* have been easier, but doing it this way should be faster, as it&#39;s just: a thread-local lookup, */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00700" name="l00700"></a><span class="lineno">  700</span><span class="preprocessor">    </span><span class="comment">/* a string clearing which should amount to a single length assignment internally, and finally a */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00701" name="l00701"></a><span class="lineno">  701</span><span class="preprocessor">    </span><span class="comment">/* write to an existing stream adapter, which would have been necessary regardless.  The alternative */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00702" name="l00702"></a><span class="lineno">  702</span><span class="preprocessor">    </span><span class="comment">/* would involve creating the string and the adapter machinery { locally } first -- every time. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00703" name="l00703"></a><span class="lineno">  703</span><span class="preprocessor">    </span><span class="comment">/* Update: Also, this way we get the continuous but distinct ostream state as documented in class Logger doc. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00704" name="l00704"></a><span class="lineno">  704</span><span class="preprocessor">    </span><span class="comment">/* Update 2: See to-do in FLOW_LOG_WITHOUT_CHECKING() doc header. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00705" name="l00705"></a><span class="lineno">  705</span><span class="preprocessor">    auto&amp; FLOW_LOG_DO_LOG_appender \</span></div>
<div class="line"><a id="l00706" name="l00706"></a><span class="lineno">  706</span><span class="preprocessor">      = *(Thread_local_string_appender::get_this_thread_string_appender(*FLOW_LOG_DO_LOG_logger)); \</span></div>
<div class="line"><a id="l00707" name="l00707"></a><span class="lineno">  707</span><span class="preprocessor">    auto&amp; FLOW_LOG_DO_LOG_os = *(FLOW_LOG_DO_LOG_appender.fresh_appender_ostream()); \</span></div>
<div class="line"><a id="l00708" name="l00708"></a><span class="lineno">  708</span><span class="preprocessor">    FLOW_LOG_DO_LOG_os &lt;&lt; ARG_stream_fragment &lt;&lt; flush; \</span></div>
<div class="line"><a id="l00709" name="l00709"></a><span class="lineno">  709</span><span class="preprocessor">    </span><span class="comment">/* They gave us all the pieces of Msg_metadata, so we just put the object together. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00710" name="l00710"></a><span class="lineno">  710</span><span class="preprocessor">    Msg_metadata* FLOW_LOG_DO_LOG_msg_metadata_ptr; \</span></div>
<div class="line"><a id="l00711" name="l00711"></a><span class="lineno">  711</span><span class="preprocessor">    if (FLOW_LOG_DO_LOG_logger-&gt;logs_asynchronously()) \</span></div>
<div class="line"><a id="l00712" name="l00712"></a><span class="lineno">  712</span><span class="preprocessor">    { \</span></div>
<div class="line"><a id="l00713" name="l00713"></a><span class="lineno">  713</span><span class="preprocessor">      </span><span class="comment">/* () used to avoid nested-macro-comma trouble. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00714" name="l00714"></a><span class="lineno">  714</span><span class="preprocessor">      (FLOW_LOG_DO_LOG_msg_metadata_ptr \</span></div>
<div class="line"><a id="l00715" name="l00715"></a><span class="lineno">  715</span><span class="preprocessor">         = new Msg_metadata{ ARG_component, ARG_sev, ARG_file_view, ARG_line, ARG_func_view, \</span></div>
<div class="line"><a id="l00716" name="l00716"></a><span class="lineno">  716</span><span class="preprocessor">                             ARG_time_stamp, std::move(ARG_call_thread_nickname_str_moved), ARG_call_thread_id }); \</span></div>
<div class="line"><a id="l00717" name="l00717"></a><span class="lineno">  717</span><span class="preprocessor">      </span><span class="comment">/* FLOW_LOG_DO_LOG_msg_metadata_ptr will be async-deleted by Logger (see below). */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00718" name="l00718"></a><span class="lineno">  718</span><span class="preprocessor">    } \</span></div>
<div class="line"><a id="l00719" name="l00719"></a><span class="lineno">  719</span><span class="preprocessor">    else \</span></div>
<div class="line"><a id="l00720" name="l00720"></a><span class="lineno">  720</span><span class="preprocessor">    { \</span></div>
<div class="line"><a id="l00721" name="l00721"></a><span class="lineno">  721</span><span class="preprocessor">      FLOW_LOG_DO_LOG_msg_metadata_ptr = this_thread_sync_msg_metadata_ptr.get(); \</span></div>
<div class="line"><a id="l00722" name="l00722"></a><span class="lineno">  722</span><span class="preprocessor">      if (!FLOW_LOG_DO_LOG_msg_metadata_ptr) \</span></div>
<div class="line"><a id="l00723" name="l00723"></a><span class="lineno">  723</span><span class="preprocessor">      { </span><span class="comment">/* This happens once per thread at most. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00724" name="l00724"></a><span class="lineno">  724</span><span class="preprocessor">        this_thread_sync_msg_metadata_ptr.reset(FLOW_LOG_DO_LOG_msg_metadata_ptr = new Msg_metadata); \</span></div>
<div class="line"><a id="l00725" name="l00725"></a><span class="lineno">  725</span><span class="preprocessor">      } \</span></div>
<div class="line"><a id="l00726" name="l00726"></a><span class="lineno">  726</span><span class="preprocessor">      </span><span class="comment">/* () used to avoid nested-macro-comma trouble. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00727" name="l00727"></a><span class="lineno">  727</span><span class="preprocessor">      ((*FLOW_LOG_DO_LOG_msg_metadata_ptr) \</span></div>
<div class="line"><a id="l00728" name="l00728"></a><span class="lineno">  728</span><span class="preprocessor">         = { ARG_component, ARG_sev, ARG_file_view, ARG_line, ARG_func_view, \</span></div>
<div class="line"><a id="l00729" name="l00729"></a><span class="lineno">  729</span><span class="preprocessor">             ARG_time_stamp, std::move(ARG_call_thread_nickname_str_moved), ARG_call_thread_id }); \</span></div>
<div class="line"><a id="l00730" name="l00730"></a><span class="lineno">  730</span><span class="preprocessor">      </span><span class="comment">/* *FLOW_LOG_DO_LOG_msg_metadata_ptr will be overwritten next time in this thread, and again and again. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00731" name="l00731"></a><span class="lineno">  731</span><span class="preprocessor">    } \</span></div>
<div class="line"><a id="l00732" name="l00732"></a><span class="lineno">  732</span><span class="preprocessor">    </span><span class="comment">/* Time to log it finally and (if applicable) clean up. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00733" name="l00733"></a><span class="lineno">  733</span><span class="preprocessor">    </span><span class="comment">/* Asynchronous path (see above `if`): */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00734" name="l00734"></a><span class="lineno">  734</span><span class="preprocessor">    </span><span class="comment">/*   target_contents() returns const reference that we pass through without copying. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00735" name="l00735"></a><span class="lineno">  735</span><span class="preprocessor">    </span><span class="comment">/*   However, FLOW_LOG_DO_LOG_logger with true logs_asynchronously() knows it needs to make a copy of this to */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00736" name="l00736"></a><span class="lineno">  736</span><span class="preprocessor">    </span><span class="comment">/*   log that later, asynchronously. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00737" name="l00737"></a><span class="lineno">  737</span><span class="preprocessor">    </span><span class="comment">/*   Also it specifically knows *it* must `delete` FLOW_LOG_DO_LOG_msg_metadata_ptr when done with it */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00738" name="l00738"></a><span class="lineno">  738</span><span class="preprocessor">    </span><span class="comment">/*   subsequently. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00739" name="l00739"></a><span class="lineno">  739</span><span class="preprocessor">    </span><span class="comment">/* Synchronous path: */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00740" name="l00740"></a><span class="lineno">  740</span><span class="preprocessor">    </span><span class="comment">/*   This path is simpler.  Logger won&#39;t make a copy of the message, to which we still pass a ref; */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00741" name="l00741"></a><span class="lineno">  741</span><span class="preprocessor">    </span><span class="comment">/*   and it specifically knows it must NOT `delete` FLOW_LOG_DO_LOG_msg_metadata_ptr.  */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00742" name="l00742"></a><span class="lineno">  742</span><span class="preprocessor">    </span><span class="comment">/*   However, for an alleged perf bump (@todo verify!) we use a */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00743" name="l00743"></a><span class="lineno">  743</span><span class="preprocessor">    </span><span class="comment">/*   thread-local Msg_metadata to avoid making this thing on the stack and then destroying almost immediately. */</span><span class="preprocessor"> \</span></div>
<div class="line"><a id="l00744" name="l00744"></a><span class="lineno">  744</span><span class="preprocessor">    FLOW_LOG_DO_LOG_logger-&gt;do_log(FLOW_LOG_DO_LOG_msg_metadata_ptr, \</span></div>
<div class="line"><a id="l00745" name="l00745"></a><span class="lineno">  745</span><span class="preprocessor">                                   String_view(FLOW_LOG_DO_LOG_appender.target_contents())); \</span></div>
<div class="line"><a id="l00746" name="l00746"></a><span class="lineno">  746</span><span class="preprocessor">  ) </span><span class="comment">/* FLOW_UTIL_SEMICOLON_SAFE() */</span><span class="preprocessor"></span></div>
<div class="line"><a id="l00747" name="l00747"></a><span class="lineno">  747</span> </div>
<div class="line"><a id="l00748" name="l00748"></a><span class="lineno">  748</span><span class="keyword">namespace </span><a class="code hl_namespace" href="namespaceflow_1_1log.html">flow::log</a></div>
<div class="line"><a id="l00749" name="l00749"></a><span class="lineno">  749</span>{</div>
<div class="line"><a id="l00750" name="l00750"></a><span class="lineno">  750</span><span class="comment">// Types.</span></div>
<div class="line"><a id="l00751" name="l00751"></a><span class="lineno">  751</span><span class="comment"></span> </div>
<div class="line"><a id="l00752" name="l00752"></a><span class="lineno">  752</span><span class="comment">/**</span></div>
<div class="line"><a id="l00753" name="l00753"></a><span class="lineno">  753</span><span class="comment"> * A light-weight class, each object storing a *component* payload encoding an `enum` value from `enum` type of</span></div>
<div class="line"><a id="l00754" name="l00754"></a><span class="lineno">  754</span><span class="comment"> * user&#39;s choice, and a light-weight ID of that `enum` type itself.</span></div>
<div class="line"><a id="l00755" name="l00755"></a><span class="lineno">  755</span><span class="comment"> * A Component is supplied by the user, at every logging call site, along with the message.</span></div>
<div class="line"><a id="l00756" name="l00756"></a><span class="lineno">  756</span><span class="comment"> * Log_context (or FLOW_LOG_SET_CONTEXT() in relatively rare scenarios) makes this easier, so typically user need not</span></div>
<div class="line"><a id="l00757" name="l00757"></a><span class="lineno">  757</span><span class="comment"> * literally type out a component at every logging call site, meaning there is a &quot;context&quot; that already stores it</span></div>
<div class="line"><a id="l00758" name="l00758"></a><span class="lineno">  758</span><span class="comment"> * and need not be re-specified.</span></div>
<div class="line"><a id="l00759" name="l00759"></a><span class="lineno">  759</span><span class="comment"> *</span></div>
<div class="line"><a id="l00760" name="l00760"></a><span class="lineno">  760</span><span class="comment"> * A Component can be either empty, as when default-constructed, indicated by empty() returning `true`; or non-empty,</span></div>
<div class="line"><a id="l00761" name="l00761"></a><span class="lineno">  761</span><span class="comment"> * in which case it actually stores something interesting.  In the latter case, construct it with the templated</span></div>
<div class="line"><a id="l00762" name="l00762"></a><span class="lineno">  762</span><span class="comment"> * one-arg constructor.  The template arg `Payload` must, always, be user&#39;s own `enum class`.  In order to have this</span></div>
<div class="line"><a id="l00763" name="l00763"></a><span class="lineno">  763</span><span class="comment"> * `Payload` interpreted correctly, one can (and usually should) use the log::Config facility which is used by</span></div>
<div class="line"><a id="l00764" name="l00764"></a><span class="lineno">  764</span><span class="comment"> * out-of-the-box Logger implementations including Simple_ostream_logger (useful for console output) and</span></div>
<div class="line"><a id="l00765" name="l00765"></a><span class="lineno">  765</span><span class="comment"> * Async_file_logger (for heavy-duty file logging, including rotation support).  However, this is technically optional:</span></div>
<div class="line"><a id="l00766" name="l00766"></a><span class="lineno">  766</span><span class="comment"> * one can implement their own Logger which might not use the Config facility and thus deal with the meaning of</span></div>
<div class="line"><a id="l00767" name="l00767"></a><span class="lineno">  767</span><span class="comment"> * Component in some completely different way.  I&#39;d start with an existing Logger implementation however; and if writing</span></div>
<div class="line"><a id="l00768" name="l00768"></a><span class="lineno">  768</span><span class="comment"> * one&#39;s own Logger, then still have it use log::Config, unless that system is somehow insufficient or inappropriate.</span></div>
<div class="line"><a id="l00769" name="l00769"></a><span class="lineno">  769</span><span class="comment"> *</span></div>
<div class="line"><a id="l00770" name="l00770"></a><span class="lineno">  770</span><span class="comment"> * Tip: Arguably the best way to see how to use all this together, just see flow::Flow_log_component and how Flow&#39;s own</span></div>
<div class="line"><a id="l00771" name="l00771"></a><span class="lineno">  771</span><span class="comment"> * code (which, itself, logs!) uses the log system.  This is discussed in more detail in the class Config doc header.</span></div>
<div class="line"><a id="l00772" name="l00772"></a><span class="lineno">  772</span><span class="comment"> * Lastly, some clarifying discussion may be found (as of this writing) in the Component::type_info() doc header.</span></div>
<div class="line"><a id="l00773" name="l00773"></a><span class="lineno">  773</span><span class="comment"> *</span></div>
<div class="line"><a id="l00774" name="l00774"></a><span class="lineno">  774</span><span class="comment"> * ### Thread safety, mutability ###</span></div>
<div class="line"><a id="l00775" name="l00775"></a><span class="lineno">  775</span><span class="comment"> * A Component is immutable as of this writing, except one can trivially overwrite a Component via an assignment</span></div>
<div class="line"><a id="l00776" name="l00776"></a><span class="lineno">  776</span><span class="comment"> * operator.  The latter write operation is not thread-safe w.r.t. a given `*this`, though in practice this is unlikely</span></div>
<div class="line"><a id="l00777" name="l00777"></a><span class="lineno">  777</span><span class="comment"> * to ever matter.</span></div>
<div class="line"><a id="l00778" name="l00778"></a><span class="lineno">  778</span><span class="comment"> *</span></div>
<div class="line"><a id="l00779" name="l00779"></a><span class="lineno">  779</span><span class="comment"> * @internal</span></div>
<div class="line"><a id="l00780" name="l00780"></a><span class="lineno">  780</span><span class="comment"> *</span></div>
<div class="line"><a id="l00781" name="l00781"></a><span class="lineno">  781</span><span class="comment"> * ### Implementation discussion ###</span></div>
<div class="line"><a id="l00782" name="l00782"></a><span class="lineno">  782</span><span class="comment"> * Again -- a Component conceptually must store only 2 things:</span></div>
<div class="line"><a id="l00783" name="l00783"></a><span class="lineno">  783</span><span class="comment"> *   - Encoding of an `enum` value.</span></div>
<div class="line"><a id="l00784" name="l00784"></a><span class="lineno">  784</span><span class="comment"> *   - Some ID of the `enum class` type from which this value originates.</span></div>
<div class="line"><a id="l00785" name="l00785"></a><span class="lineno">  785</span><span class="comment"> *</span></div>
<div class="line"><a id="l00786" name="l00786"></a><span class="lineno">  786</span><span class="comment"> * Why these 2 values?</span></div>
<div class="line"><a id="l00787" name="l00787"></a><span class="lineno">  787</span><span class="comment"> *   - When a Logger logs, it will likely want to print some string representation.  If it&#39;s just printing an integer,</span></div>
<div class="line"><a id="l00788" name="l00788"></a><span class="lineno">  788</span><span class="comment"> *     then it needs that integer.  If it&#39;s printing a string, it&#39;ll probably need to look up that string; for which</span></div>
<div class="line"><a id="l00789" name="l00789"></a><span class="lineno">  789</span><span class="comment"> *     it needs the ID of the per-logging-module component table, and of course the row within that table; as</span></div>
<div class="line"><a id="l00790" name="l00790"></a><span class="lineno">  790</span><span class="comment"> *     component 2 for module A is completely not the same component at all as component 2 for module B (and if it is,</span></div>
<div class="line"><a id="l00791" name="l00791"></a><span class="lineno">  791</span><span class="comment"> *     then it is a coincidence presumably).</span></div>
<div class="line"><a id="l00792" name="l00792"></a><span class="lineno">  792</span><span class="comment"> *   - When a Logger decides *whether* component C should indeed log message M (not even constructed yet at that point,</span></div>
<div class="line"><a id="l00793" name="l00793"></a><span class="lineno">  793</span><span class="comment"> *     for perf) at log::Sev S, it must look up whether the logging of component C messages at severity S is indeed</span></div>
<div class="line"><a id="l00794" name="l00794"></a><span class="lineno">  794</span><span class="comment"> *     enabled at present.  Some kind of data structure is required; for example a map (conceptually) from C to</span></div>
<div class="line"><a id="l00795" name="l00795"></a><span class="lineno">  795</span><span class="comment"> *     max severity S&#39;, to compare S vs. S&#39;.  log::Config (technically optional, though all out-of-the-box `Logger`s</span></div>
<div class="line"><a id="l00796" name="l00796"></a><span class="lineno">  796</span><span class="comment"> *     do use it), in particular, has such a structure.</span></div>
<div class="line"><a id="l00797" name="l00797"></a><span class="lineno">  797</span><span class="comment"> *</span></div>
<div class="line"><a id="l00798" name="l00798"></a><span class="lineno">  798</span><span class="comment"> * The operations required to implement, then, are:</span></div>
<div class="line"><a id="l00799" name="l00799"></a><span class="lineno">  799</span><span class="comment"> *   - Construct a Component from an `enum class` value of arbitrary type (one such type per logging module).</span></div>
<div class="line"><a id="l00800" name="l00800"></a><span class="lineno">  800</span><span class="comment"> *   - Access the type ID of the latter type.</span></div>
<div class="line"><a id="l00801" name="l00801"></a><span class="lineno">  801</span><span class="comment"> *   - Access the `enum` value itself.</span></div>
<div class="line"><a id="l00802" name="l00802"></a><span class="lineno">  802</span><span class="comment"> *</span></div>
<div class="line"><a id="l00803" name="l00803"></a><span class="lineno">  803</span><span class="comment"> * The first version of Component did this by simply storing (and thus being, in terms of data, equal to) `boost::any`.</span></div>
<div class="line"><a id="l00804" name="l00804"></a><span class="lineno">  804</span><span class="comment"> * The constructor would simply load the `enum` value of type T as the `any` payload.  The accessors would</span></div>
<div class="line"><a id="l00805" name="l00805"></a><span class="lineno">  805</span><span class="comment"> * `any_cast&lt;T&gt;()` and then trivially access the value itself and/or its `typeid()`.</span></div>
<div class="line"><a id="l00806" name="l00806"></a><span class="lineno">  806</span><span class="comment"> *</span></div>
<div class="line"><a id="l00807" name="l00807"></a><span class="lineno">  807</span><span class="comment"> * This was delightful in terms of code simplicity.  However, due to the extreme prevalence of Logger::should_log()</span></div>
<div class="line"><a id="l00808" name="l00808"></a><span class="lineno">  808</span><span class="comment"> * checks in code -- at *every* log call site, including high-verbosity ones that do *not* typically result in</span></div>
<div class="line"><a id="l00809" name="l00809"></a><span class="lineno">  809</span><span class="comment"> * messages being logged, such as for Sev::S_TRACE -- certain perf aspects of `boost::any` involved non-trivial perf</span></div>
<div class="line"><a id="l00810" name="l00810"></a><span class="lineno">  810</span><span class="comment"> * costs.  Namely:</span></div>
<div class="line"><a id="l00811" name="l00811"></a><span class="lineno">  811</span><span class="comment"> *   - `any` constructor performs a `new` when storing the arbitrarily-typed value, even though in our case it&#39;s</span></div>
<div class="line"><a id="l00812" name="l00812"></a><span class="lineno">  812</span><span class="comment"> *     always just an `enum`.  Copying an `any` similarly will need to `new`.</span></div>
<div class="line"><a id="l00813" name="l00813"></a><span class="lineno">  813</span><span class="comment"> *   - The `any` accessors must do `virtual` lookups, to resolve to the particular `enum class` type.</span></div>
<div class="line"><a id="l00814" name="l00814"></a><span class="lineno">  814</span><span class="comment"> *</span></div>
<div class="line"><a id="l00815" name="l00815"></a><span class="lineno">  815</span><span class="comment"> * Hence the current solution optimized those issues away by making use of the fact we know the stored thing is</span></div>
<div class="line"><a id="l00816" name="l00816"></a><span class="lineno">  816</span><span class="comment"> * *always* an `enum class`.  Hence:</span></div>
<div class="line"><a id="l00817" name="l00817"></a><span class="lineno">  817</span><span class="comment"> *   - Its value can be stored as an integer.</span></div>
<div class="line"><a id="l00818" name="l00818"></a><span class="lineno">  818</span><span class="comment"> *   - Its type can be stored directly; and since the type is an `enum`, which is non-polymorphic, the `typeid()`</span></div>
<div class="line"><a id="l00819" name="l00819"></a><span class="lineno">  819</span><span class="comment"> *     operation does not even need to do the `virtual` resolution.  In fact its result is known at compile time.</span></div>
<div class="line"><a id="l00820" name="l00820"></a><span class="lineno">  820</span><span class="comment"> *     (This can even lead to further optimizations by the compiler.)</span></div>
<div class="line"><a id="l00821" name="l00821"></a><span class="lineno">  821</span><span class="comment"> *</span></div>
<div class="line"><a id="l00822" name="l00822"></a><span class="lineno">  822</span><span class="comment"> * Some discussion for perspective:</span></div>
<div class="line"><a id="l00823" name="l00823"></a><span class="lineno">  823</span><span class="comment"> *   - Using `any` was elegant in terms of code simplicity; it is analogous to runtime dynamic typing of languages</span></div>
<div class="line"><a id="l00824" name="l00824"></a><span class="lineno">  824</span><span class="comment"> *     like Python.</span></div>
<div class="line"><a id="l00825" name="l00825"></a><span class="lineno">  825</span><span class="comment"> *   - It is just that it was too slow given the frequency of the accessor operations (and, to a lesser but still</span></div>
<div class="line"><a id="l00826" name="l00826"></a><span class="lineno">  826</span><span class="comment"> *     potentially significant degree -- as with FLOW_LOG_SET_CONTEXT() -- for construction/copying).</span></div>
<div class="line"><a id="l00827" name="l00827"></a><span class="lineno">  827</span><span class="comment"> *   - Therefore it was replaced by a less-pithy hand-optimized solution that doesn&#39;t use Python-style dynamic typing</span></div>
<div class="line"><a id="l00828" name="l00828"></a><span class="lineno">  828</span><span class="comment"> *     but instead encodes the 2 bits of info directly by using the fact it&#39;s always an `enum`.</span></div>
<div class="line"><a id="l00829" name="l00829"></a><span class="lineno">  829</span><span class="comment"> *   - This does not mean `boost::any` is just too slow, because most operations are not done</span></div>
<div class="line"><a id="l00830" name="l00830"></a><span class="lineno">  830</span><span class="comment"> *     as frequently as should-log checks.  It *does* mean it may be too slow in production in this *particular*</span></div>
<div class="line"><a id="l00831" name="l00831"></a><span class="lineno">  831</span><span class="comment"> *     context.</span></div>
<div class="line"><a id="l00832" name="l00832"></a><span class="lineno">  832</span><span class="comment"> *     - It has been alleged that `std::any` (appearing first in C++17) in some or all gcc versions optimized-away these</span></div>
<div class="line"><a id="l00833" name="l00833"></a><span class="lineno">  833</span><span class="comment"> *       perf problems by storing certain values directly inside it, when those values were small enough to &quot;fit.&quot;</span></div>
<div class="line"><a id="l00834" name="l00834"></a><span class="lineno">  834</span><span class="comment"> *       (Our `enum`s presumably would fit that bill, being glorified `int`s.)  This is believable: Many `std::string`</span></div>
<div class="line"><a id="l00835" name="l00835"></a><span class="lineno">  835</span><span class="comment"> *       impls will directly store strings of sufficiently small length; e.g., &lt;=15 bytes would fit into the same area</span></div>
<div class="line"><a id="l00836" name="l00836"></a><span class="lineno">  836</span><span class="comment"> *       as the pointers and length data members required for arbitrarily-long string that do require heap allocation.</span></div>
<div class="line"><a id="l00837" name="l00837"></a><span class="lineno">  837</span><span class="comment"> *       Probably the same can be done for `any`.  So keep that in mind if using `any` functionality in other contexts.</span></div>
<div class="line"><a id="l00838" name="l00838"></a><span class="lineno">  838</span><span class="comment"> */</span></div>
<div class="line"><a id="l00839" name="l00839"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Component.html">  839</a></span><span class="keyword">class </span><a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a></div>
<div class="line"><a id="l00840" name="l00840"></a><span class="lineno">  840</span>{</div>
<div class="line"><a id="l00841" name="l00841"></a><span class="lineno">  841</span><span class="keyword">public</span>:</div>
<div class="line"><a id="l00842" name="l00842"></a><span class="lineno">  842</span>  <span class="comment">// Types.</span></div>
<div class="line"><a id="l00843" name="l00843"></a><span class="lineno">  843</span><span class="comment"></span> </div>
<div class="line"><a id="l00844" name="l00844"></a><span class="lineno">  844</span><span class="comment">  /// The type `Payload` must be `enum class Payload : enum_raw_t`: an `enum` type encoded via this integer type.</span></div>
<div class="line"><a id="l00845" name="l00845"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Component.html#a287888e2943b312f4febc3e8e130fc80">  845</a></span><span class="comment"></span>  <span class="keyword">using </span><a class="code hl_typedef" href="classflow_1_1log_1_1Component.html#a287888e2943b312f4febc3e8e130fc80">enum_raw_t</a> = <span class="keywordtype">unsigned</span> int;</div>
<div class="line"><a id="l00846" name="l00846"></a><span class="lineno">  846</span> </div>
<div class="line"><a id="l00847" name="l00847"></a><span class="lineno">  847</span>  <span class="comment">// Constructors/destructor.</span></div>
<div class="line"><a id="l00848" name="l00848"></a><span class="lineno">  848</span><span class="comment"></span> </div>
<div class="line"><a id="l00849" name="l00849"></a><span class="lineno">  849</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00850" name="l00850"></a><span class="lineno">  850</span><span class="comment">   * Constructs a Component that stores no payload; meaning an unspecified-component Component that returns</span></div>
<div class="line"><a id="l00851" name="l00851"></a><span class="lineno">  851</span><span class="comment">   * `empty() == true`.  Every Logger and all other systems must accept a message with such a null Component.</span></div>
<div class="line"><a id="l00852" name="l00852"></a><span class="lineno">  852</span><span class="comment">   * However, one can configure a given Logger to ensure such messages not be logged (filtered out via `should_log()`).</span></div>
<div class="line"><a id="l00853" name="l00853"></a><span class="lineno">  853</span><span class="comment">   * Point is, any log call site that supplied a null Component must still work, meaning not cause undefined behavior.</span></div>
<div class="line"><a id="l00854" name="l00854"></a><span class="lineno">  854</span><span class="comment">   */</span></div>
<div class="line"><a id="l00855" name="l00855"></a><span class="lineno">  855</span>  <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a8c746035d0eea4a26d0982eabf63b713">Component</a>();</div>
<div class="line"><a id="l00856" name="l00856"></a><span class="lineno">  856</span><span class="comment"></span> </div>
<div class="line"><a id="l00857" name="l00857"></a><span class="lineno">  857</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00858" name="l00858"></a><span class="lineno">  858</span><span class="comment">   * Constructs a Component with the given payload of arbitrary type, so long as that type is an</span></div>
<div class="line"><a id="l00859" name="l00859"></a><span class="lineno">  859</span><span class="comment">   * `enum class : Component::enum_raw_t`.  (#enum_raw_t is an unsigned integer type.)</span></div>
<div class="line"><a id="l00860" name="l00860"></a><span class="lineno">  860</span><span class="comment">   * The resulting Component will return `empty() == false`.</span></div>
<div class="line"><a id="l00861" name="l00861"></a><span class="lineno">  861</span><span class="comment">   *</span></div>
<div class="line"><a id="l00862" name="l00862"></a><span class="lineno">  862</span><span class="comment">   * @tparam Payload</span></div>
<div class="line"><a id="l00863" name="l00863"></a><span class="lineno">  863</span><span class="comment">   *         The type of the component value stored inside `*this`.  This is required to be a type satisfying</span></div>
<div class="line"><a id="l00864" name="l00864"></a><span class="lineno">  864</span><span class="comment">   *         the requirements in the doc header for #enum_raw_t.</span></div>
<div class="line"><a id="l00865" name="l00865"></a><span class="lineno">  865</span><span class="comment">   * @param payload</span></div>
<div class="line"><a id="l00866" name="l00866"></a><span class="lineno">  866</span><span class="comment">   *        The payload value copied into `*this` and whenever a Component itself is copied (or moved).</span></div>
<div class="line"><a id="l00867" name="l00867"></a><span class="lineno">  867</span><span class="comment">   */</span></div>
<div class="line"><a id="l00868" name="l00868"></a><span class="lineno">  868</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> Payload&gt;</div>
<div class="line"><a id="l00869" name="l00869"></a><span class="lineno">  869</span>  <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a8c746035d0eea4a26d0982eabf63b713">Component</a>(Payload <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a656f5868adbd8c58c493981fe1764699">payload</a>);</div>
<div class="line"><a id="l00870" name="l00870"></a><span class="lineno">  870</span><span class="comment"></span> </div>
<div class="line"><a id="l00871" name="l00871"></a><span class="lineno">  871</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00872" name="l00872"></a><span class="lineno">  872</span><span class="comment">   * Copies the source Component into `*this`.  This involves a single payload copy (and not even that if</span></div>
<div class="line"><a id="l00873" name="l00873"></a><span class="lineno">  873</span><span class="comment">   * `src.empty()`).</span></div>
<div class="line"><a id="l00874" name="l00874"></a><span class="lineno">  874</span><span class="comment">   *</span></div>
<div class="line"><a id="l00875" name="l00875"></a><span class="lineno">  875</span><span class="comment">   * @param src</span></div>
<div class="line"><a id="l00876" name="l00876"></a><span class="lineno">  876</span><span class="comment">   *        Object to copy.</span></div>
<div class="line"><a id="l00877" name="l00877"></a><span class="lineno">  877</span><span class="comment">   */</span></div>
<div class="line"><a id="l00878" name="l00878"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Component.html#a5edb4c020c9de20e4c1c96c460b624e8">  878</a></span>  <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a5edb4c020c9de20e4c1c96c460b624e8">Component</a>(<span class="keyword">const</span> <a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a>&amp; src);</div>
<div class="line"><a id="l00879" name="l00879"></a><span class="lineno">  879</span><span class="comment"></span> </div>
<div class="line"><a id="l00880" name="l00880"></a><span class="lineno">  880</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00881" name="l00881"></a><span class="lineno">  881</span><span class="comment">   * Constructs `*this` equal to `src_moved`.  In this implementation it is equivalent to the copy constructor.</span></div>
<div class="line"><a id="l00882" name="l00882"></a><span class="lineno">  882</span><span class="comment">   *</span></div>
<div class="line"><a id="l00883" name="l00883"></a><span class="lineno">  883</span><span class="comment">   * @param src_moved</span></div>
<div class="line"><a id="l00884" name="l00884"></a><span class="lineno">  884</span><span class="comment">   *        Object to move.</span></div>
<div class="line"><a id="l00885" name="l00885"></a><span class="lineno">  885</span><span class="comment">   */</span></div>
<div class="line"><a id="l00886" name="l00886"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Component.html#a325e56b14d7ce51ea4ee3cdfe6189490">  886</a></span>  <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a325e56b14d7ce51ea4ee3cdfe6189490">Component</a>(<a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a>&amp;&amp; src_moved);</div>
<div class="line"><a id="l00887" name="l00887"></a><span class="lineno">  887</span> </div>
<div class="line"><a id="l00888" name="l00888"></a><span class="lineno">  888</span>  <span class="comment">// Methods.</span></div>
<div class="line"><a id="l00889" name="l00889"></a><span class="lineno">  889</span><span class="comment"></span> </div>
<div class="line"><a id="l00890" name="l00890"></a><span class="lineno">  890</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00891" name="l00891"></a><span class="lineno">  891</span><span class="comment">   * Overwrites `*this` with a copy of `src`.</span></div>
<div class="line"><a id="l00892" name="l00892"></a><span class="lineno">  892</span><span class="comment">   * @param src</span></div>
<div class="line"><a id="l00893" name="l00893"></a><span class="lineno">  893</span><span class="comment">   *        Object to copy.</span></div>
<div class="line"><a id="l00894" name="l00894"></a><span class="lineno">  894</span><span class="comment">   * @return `*this`.</span></div>
<div class="line"><a id="l00895" name="l00895"></a><span class="lineno">  895</span><span class="comment">   */</span></div>
<div class="line"><a id="l00896" name="l00896"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Component.html#a146ce02cc7422b3a3bca07533536450e">  896</a></span>  <a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a>&amp; <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a146ce02cc7422b3a3bca07533536450e">operator=</a>(<span class="keyword">const</span> <a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a>&amp; src);</div>
<div class="line"><a id="l00897" name="l00897"></a><span class="lineno">  897</span><span class="comment"></span> </div>
<div class="line"><a id="l00898" name="l00898"></a><span class="lineno">  898</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00899" name="l00899"></a><span class="lineno">  899</span><span class="comment">   * Equivalent to `operator=(Component&lt;Payload&gt;(new_payload))` modulo possibly minor perf differences.</span></div>
<div class="line"><a id="l00900" name="l00900"></a><span class="lineno">  900</span><span class="comment">   *</span></div>
<div class="line"><a id="l00901" name="l00901"></a><span class="lineno">  901</span><span class="comment">   * @param new_payload</span></div>
<div class="line"><a id="l00902" name="l00902"></a><span class="lineno">  902</span><span class="comment">   *        See non-default constructor.</span></div>
<div class="line"><a id="l00903" name="l00903"></a><span class="lineno">  903</span><span class="comment">   * @return `*this`.</span></div>
<div class="line"><a id="l00904" name="l00904"></a><span class="lineno">  904</span><span class="comment">   */</span></div>
<div class="line"><a id="l00905" name="l00905"></a><span class="lineno">  905</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> Payload&gt;</div>
<div class="line"><a id="l00906" name="l00906"></a><span class="lineno">  906</span>  <a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a>&amp; <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a146ce02cc7422b3a3bca07533536450e">operator=</a>(Payload new_payload);</div>
<div class="line"><a id="l00907" name="l00907"></a><span class="lineno">  907</span><span class="comment"></span> </div>
<div class="line"><a id="l00908" name="l00908"></a><span class="lineno">  908</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00909" name="l00909"></a><span class="lineno">  909</span><span class="comment">   * Makes `*this` equal to `src_moved`.  In this implementation it is equivalent to copy assignment.</span></div>
<div class="line"><a id="l00910" name="l00910"></a><span class="lineno">  910</span><span class="comment">   * @param src_moved</span></div>
<div class="line"><a id="l00911" name="l00911"></a><span class="lineno">  911</span><span class="comment">   *        Object to move.</span></div>
<div class="line"><a id="l00912" name="l00912"></a><span class="lineno">  912</span><span class="comment">   * @return `*this`.</span></div>
<div class="line"><a id="l00913" name="l00913"></a><span class="lineno">  913</span><span class="comment">   */</span></div>
<div class="line"><a id="l00914" name="l00914"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Component.html#a78dc45840c6fb12bd53784f7ea277ab4">  914</a></span>  <a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a>&amp; <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a78dc45840c6fb12bd53784f7ea277ab4">operator=</a>(<a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a>&amp;&amp; src_moved);</div>
<div class="line"><a id="l00915" name="l00915"></a><span class="lineno">  915</span><span class="comment"></span> </div>
<div class="line"><a id="l00916" name="l00916"></a><span class="lineno">  916</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00917" name="l00917"></a><span class="lineno">  917</span><span class="comment">   * Returns `true` if `*this` is as if default-constructed (a null Component); `false` if as if</span></div>
<div class="line"><a id="l00918" name="l00918"></a><span class="lineno">  918</span><span class="comment">   * constructed via the 1-arg constructor (a non-null Component).</span></div>
<div class="line"><a id="l00919" name="l00919"></a><span class="lineno">  919</span><span class="comment">   *</span></div>
<div class="line"><a id="l00920" name="l00920"></a><span class="lineno">  920</span><span class="comment">   * @return See above.</span></div>
<div class="line"><a id="l00921" name="l00921"></a><span class="lineno">  921</span><span class="comment">   */</span></div>
<div class="line"><a id="l00922" name="l00922"></a><span class="lineno">  922</span>  <span class="keywordtype">bool</span> <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a5af2f66731c407bd519a873706bd04c4">empty</a>() <span class="keyword">const</span>;</div>
<div class="line"><a id="l00923" name="l00923"></a><span class="lineno">  923</span><span class="comment"></span> </div>
<div class="line"><a id="l00924" name="l00924"></a><span class="lineno">  924</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00925" name="l00925"></a><span class="lineno">  925</span><span class="comment">   * Returns reference to immutable payload stored in `*this`; undefined behavior if `empty() == true`.</span></div>
<div class="line"><a id="l00926" name="l00926"></a><span class="lineno">  926</span><span class="comment">   *</span></div>
<div class="line"><a id="l00927" name="l00927"></a><span class="lineno">  927</span><span class="comment">   * @tparam Payload</span></div>
<div class="line"><a id="l00928" name="l00928"></a><span class="lineno">  928</span><span class="comment">   *         See one-arg ctor doc header.</span></div>
<div class="line"><a id="l00929" name="l00929"></a><span class="lineno">  929</span><span class="comment">   * @return See above.</span></div>
<div class="line"><a id="l00930" name="l00930"></a><span class="lineno">  930</span><span class="comment">   */</span></div>
<div class="line"><a id="l00931" name="l00931"></a><span class="lineno">  931</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> Payload&gt;</div>
<div class="line"><a id="l00932" name="l00932"></a><span class="lineno">  932</span>  Payload <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a656f5868adbd8c58c493981fe1764699">payload</a>() <span class="keyword">const</span>;</div>
<div class="line"><a id="l00933" name="l00933"></a><span class="lineno">  933</span><span class="comment"></span> </div>
<div class="line"><a id="l00934" name="l00934"></a><span class="lineno">  934</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00935" name="l00935"></a><span class="lineno">  935</span><span class="comment">   * Returns `typeid(Payload)`, where `Payload` was the template param used when calling the</span></div>
<div class="line"><a id="l00936" name="l00936"></a><span class="lineno">  936</span><span class="comment">   * originating one-arg constructor or equivalent; undefined behavior if `empty() == true`.</span></div>
<div class="line"><a id="l00937" name="l00937"></a><span class="lineno">  937</span><span class="comment">   *</span></div>
<div class="line"><a id="l00938" name="l00938"></a><span class="lineno">  938</span><span class="comment">   * flow::log user that relies fully on an out-of-the-box Logger, or on a custom Logger that</span></div>
<div class="line"><a id="l00939" name="l00939"></a><span class="lineno">  939</span><span class="comment">   * nevertheless fully uses the log::Config facility, is unlikely to need this information.</span></div>
<div class="line"><a id="l00940" name="l00940"></a><span class="lineno">  940</span><span class="comment">   * (It is used internally by log::Config.)  However, a custom Logger that decided to use</span></div>
<div class="line"><a id="l00941" name="l00941"></a><span class="lineno">  941</span><span class="comment">   * an alternative Component mechanism (as opposed to how log::Config and reliant `Logger`s do)</span></div>
<div class="line"><a id="l00942" name="l00942"></a><span class="lineno">  942</span><span class="comment">   * can use this payload_type() method to distinguish between potential source `enum`s that were</span></div>
<div class="line"><a id="l00943" name="l00943"></a><span class="lineno">  943</span><span class="comment">   * passed to the Logger at each given log call site.</span></div>
<div class="line"><a id="l00944" name="l00944"></a><span class="lineno">  944</span><span class="comment">   *</span></div>
<div class="line"><a id="l00945" name="l00945"></a><span class="lineno">  945</span><span class="comment">   * For example, consider that Flow itself, for its own logging, uses the flow::Flow_log_component</span></div>
<div class="line"><a id="l00946" name="l00946"></a><span class="lineno">  946</span><span class="comment">   * `enum` at all log call sites.  Imagine you, the user, have decided to generate your own</span></div>
<div class="line"><a id="l00947" name="l00947"></a><span class="lineno">  947</span><span class="comment">   * flow::log messages and always use your own `enum class cool_project::Cool_log_component` at your</span></div>
<div class="line"><a id="l00948" name="l00948"></a><span class="lineno">  948</span><span class="comment">   * own logging call sites.  Then, a typical component specification will look like this respectively:</span></div>
<div class="line"><a id="l00949" name="l00949"></a><span class="lineno">  949</span><span class="comment">   *</span></div>
<div class="line"><a id="l00950" name="l00950"></a><span class="lineno">  950</span><span class="comment">   *   ~~~</span></div>
<div class="line"><a id="l00951" name="l00951"></a><span class="lineno">  951</span><span class="comment">   *   class flow::net_flow::Node : public Log_context</span></div>
<div class="line"><a id="l00952" name="l00952"></a><span class="lineno">  952</span><span class="comment">   *   {</span></div>
<div class="line"><a id="l00953" name="l00953"></a><span class="lineno">  953</span><span class="comment">   *     Node(...) :</span></div>
<div class="line"><a id="l00954" name="l00954"></a><span class="lineno">  954</span><span class="comment">   *       Log_context(..., Flow_log_component::S_NET_FLOW) // This class will usually use the NET_FLOW component.</span></div>
<div class="line"><a id="l00955" name="l00955"></a><span class="lineno">  955</span><span class="comment">   *       ...</span></div>
<div class="line"><a id="l00956" name="l00956"></a><span class="lineno">  956</span><span class="comment">   *</span></div>
<div class="line"><a id="l00957" name="l00957"></a><span class="lineno">  957</span><span class="comment">   *   class cool_project::Cool_class_about_widgets : public Log_context</span></div>
<div class="line"><a id="l00958" name="l00958"></a><span class="lineno">  958</span><span class="comment">   *   {</span></div>
<div class="line"><a id="l00959" name="l00959"></a><span class="lineno">  959</span><span class="comment">   *     Cool_class_about_widgets(...) :</span></div>
<div class="line"><a id="l00960" name="l00960"></a><span class="lineno">  960</span><span class="comment">   *       Log_context(..., Cool_log_component::S_WIDGETRY) // Ditto for your own code.  Use your own enum.</span></div>
<div class="line"><a id="l00961" name="l00961"></a><span class="lineno">  961</span><span class="comment">   *   ~~~</span></div>
<div class="line"><a id="l00962" name="l00962"></a><span class="lineno">  962</span><span class="comment">   *</span></div>
<div class="line"><a id="l00963" name="l00963"></a><span class="lineno">  963</span><span class="comment">   * Now, `this-&gt;get_log_component().payload_type()` will equal that of `Flow_log_component` and `Cool_log_component`,</span></div>
<div class="line"><a id="l00964" name="l00964"></a><span class="lineno">  964</span><span class="comment">   * respectively, within those 2 classes.  In particular, a custom Logger implementation can use `payload_type()`</span></div>
<div class="line"><a id="l00965" name="l00965"></a><span class="lineno">  965</span><span class="comment">   * to interpret the `Component`s of values from the 2</span></div>
<div class="line"><a id="l00966" name="l00966"></a><span class="lineno">  966</span><span class="comment">   * entirely disparate `enum`s in different ways.  More in particular, the out-of-the-box `Logger`s use `Config`</span></div>
<div class="line"><a id="l00967" name="l00967"></a><span class="lineno">  967</span><span class="comment">   * to do all of that without your having to worry about it (but your own Logger would potentially have to worry</span></div>
<div class="line"><a id="l00968" name="l00968"></a><span class="lineno">  968</span><span class="comment">   * about it particularly if not using log::Config... though we suggest that you should, barring excellent</span></div>
<div class="line"><a id="l00969" name="l00969"></a><span class="lineno">  969</span><span class="comment">   * design counter-reasons).</span></div>
<div class="line"><a id="l00970" name="l00970"></a><span class="lineno">  970</span><span class="comment">   *</span></div>
<div class="line"><a id="l00971" name="l00971"></a><span class="lineno">  971</span><span class="comment">   * @return See above.</span></div>
<div class="line"><a id="l00972" name="l00972"></a><span class="lineno">  972</span><span class="comment">   */</span></div>
<div class="line"><a id="l00973" name="l00973"></a><span class="lineno">  973</span>  <span class="keyword">const</span> std::type_info&amp; <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a3ff8ff4d75add447b3e10ded5430833d">payload_type</a>() <span class="keyword">const</span>;</div>
<div class="line"><a id="l00974" name="l00974"></a><span class="lineno">  974</span><span class="comment"></span> </div>
<div class="line"><a id="l00975" name="l00975"></a><span class="lineno">  975</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00976" name="l00976"></a><span class="lineno">  976</span><span class="comment">   * Returns the numeric value of the `enum` payload stored by this Component, originating in the one-arg constructor;</span></div>
<div class="line"><a id="l00977" name="l00977"></a><span class="lineno">  977</span><span class="comment">   * undefined behavior if `empty() == true`.</span></div>
<div class="line"><a id="l00978" name="l00978"></a><span class="lineno">  978</span><span class="comment">   *</span></div>
<div class="line"><a id="l00979" name="l00979"></a><span class="lineno">  979</span><span class="comment">   * @return See above.  Specifically that&#39;s: `static_cast&lt;enum_raw_t&gt;(payload)`, where `payload` was passed to</span></div>
<div class="line"><a id="l00980" name="l00980"></a><span class="lineno">  980</span><span class="comment">   *         originating 1-arg ctor.</span></div>
<div class="line"><a id="l00981" name="l00981"></a><span class="lineno">  981</span><span class="comment">   */</span></div>
<div class="line"><a id="l00982" name="l00982"></a><span class="lineno">  982</span>  <a class="code hl_typedef" href="classflow_1_1log_1_1Component.html#a287888e2943b312f4febc3e8e130fc80">enum_raw_t</a> <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a899a7d2b0c5daa8e4d666d431b9bf48e">payload_enum_raw_value</a>() <span class="keyword">const</span>;</div>
<div class="line"><a id="l00983" name="l00983"></a><span class="lineno">  983</span> </div>
<div class="line"><a id="l00984" name="l00984"></a><span class="lineno">  984</span><span class="keyword">private</span>:</div>
<div class="line"><a id="l00985" name="l00985"></a><span class="lineno">  985</span>  <span class="comment">// Data.</span></div>
<div class="line"><a id="l00986" name="l00986"></a><span class="lineno">  986</span><span class="comment"></span> </div>
<div class="line"><a id="l00987" name="l00987"></a><span class="lineno">  987</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00988" name="l00988"></a><span class="lineno">  988</span><span class="comment">   * The `typeid()` of the `Payload` passed to the 1-arg constructor; if 0-arg ctor was used (empty() is `true`) then</span></div>
<div class="line"><a id="l00989" name="l00989"></a><span class="lineno">  989</span><span class="comment">   * it is null.</span></div>
<div class="line"><a id="l00990" name="l00990"></a><span class="lineno">  990</span><span class="comment">   *</span></div>
<div class="line"><a id="l00991" name="l00991"></a><span class="lineno">  991</span><span class="comment">   * ### Rationale ###</span></div>
<div class="line"><a id="l00992" name="l00992"></a><span class="lineno">  992</span><span class="comment">   * Why is it a pointer and not something else?  Answer:</span></div>
<div class="line"><a id="l00993" name="l00993"></a><span class="lineno">  993</span><span class="comment">   * It cannot be a direct member: `type_info` is not copyable.  It cannot be a non-`const` reference for the</span></div>
<div class="line"><a id="l00994" name="l00994"></a><span class="lineno">  994</span><span class="comment">   * same reason.  It cannot be a `const` reference, because Component is mutable via assignment.</span></div>
<div class="line"><a id="l00995" name="l00995"></a><span class="lineno">  995</span><span class="comment">   * Could use `reference_wrapper&lt;const type_info&gt;`, but ultimately that&#39;s the same as storing a pointer.</span></div>
<div class="line"><a id="l00996" name="l00996"></a><span class="lineno">  996</span><span class="comment">   *</span></div>
<div class="line"><a id="l00997" name="l00997"></a><span class="lineno">  997</span><span class="comment">   * In any case by definition `type_info` is not copyable, and indeed the desire to store a &quot;copy&quot; is wrong-headed.</span></div>
<div class="line"><a id="l00998" name="l00998"></a><span class="lineno">  998</span><span class="comment">   *</span></div>
<div class="line"><a id="l00999" name="l00999"></a><span class="lineno">  999</span><span class="comment">   * ### Discussion of performance ###</span></div>
<div class="line"><a id="l01000" name="l01000"></a><span class="lineno"> 1000</span><span class="comment">   * Careful: This does not mean that (for `type_info`s `A` and `B`)</span></div>
<div class="line"><a id="l01001" name="l01001"></a><span class="lineno"> 1001</span><span class="comment">   * `A == B` only if `&amp;A == &amp;B`: two `type_info`s may be equal -- refer to the</span></div>
<div class="line"><a id="l01002" name="l01002"></a><span class="lineno"> 1002</span><span class="comment">   * same type -- but be distinct objects.  This occurs essentially only if the `A = typeid(...)` op</span></div>
<div class="line"><a id="l01003" name="l01003"></a><span class="lineno"> 1003</span><span class="comment">   * was done on another side of a shared-object boundary versus the `B = typeid(...)` op.</span></div>
<div class="line"><a id="l01004" name="l01004"></a><span class="lineno"> 1004</span><span class="comment">   *</span></div>
<div class="line"><a id="l01005" name="l01005"></a><span class="lineno"> 1005</span><span class="comment">   * (If they&#39;re *not* on opposing sides that way, then in fact `A == B` (if and) only if `&amp;A == &amp;B`.  For example, if</span></div>
<div class="line"><a id="l01006" name="l01006"></a><span class="lineno"> 1006</span><span class="comment">   * you&#39;ve statically-linked all relevant code, then the relevant `type_info`s will be 1-1 with their addresses</span></div>
<div class="line"><a id="l01007" name="l01007"></a><span class="lineno"> 1007</span><span class="comment">   * after all.)</span></div>
<div class="line"><a id="l01008" name="l01008"></a><span class="lineno"> 1008</span><span class="comment">   *</span></div>
<div class="line"><a id="l01009" name="l01009"></a><span class="lineno"> 1009</span><span class="comment">   * That is why `type_index` (cted from a `type_info`) is useful for (essentially) storing `type_info`s in</span></div>
<div class="line"><a id="l01010" name="l01010"></a><span class="lineno"> 1010</span><span class="comment">   * containers.  Problem is: syntactically it&#39;s great; but it can give a false sense of performance:</span></div>
<div class="line"><a id="l01011" name="l01011"></a><span class="lineno"> 1011</span><span class="comment">   * internally hashing, equality, and ordering ops cannot simply always assume `type_info*`s are 1-1 with distinct</span></div>
<div class="line"><a id="l01012" name="l01012"></a><span class="lineno"> 1012</span><span class="comment">   * `type_info`s and hence usually STLs implement the hashing in terms of `type_info::name()` -- a string, namely</span></div>
<div class="line"><a id="l01013" name="l01013"></a><span class="lineno"> 1013</span><span class="comment">   * usually one containing the entire fully qualified type name (e.g.: some mangled version of</span></div>
<div class="line"><a id="l01014" name="l01014"></a><span class="lineno"> 1014</span><span class="comment">   * `&quot;flow::Log_component&quot;`).  Utilities in detail/component_cfg.hpp work with this topic.  For more:</span></div>
<div class="line"><a id="l01015" name="l01015"></a><span class="lineno"> 1015</span><span class="comment">   * start with Config::Component_payload_type_to_cfg_map doc header.</span></div>
<div class="line"><a id="l01016" name="l01016"></a><span class="lineno"> 1016</span><span class="comment">   */</span></div>
<div class="line"><a id="l01017" name="l01017"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Component.html#a3c753f22e196c5f84718541ebb27dcac"> 1017</a></span>  std::type_info <span class="keyword">const</span> * <a class="code hl_variable" href="classflow_1_1log_1_1Component.html#a3c753f22e196c5f84718541ebb27dcac">m_payload_type_or_null</a>;</div>
<div class="line"><a id="l01018" name="l01018"></a><span class="lineno"> 1018</span><span class="comment"></span> </div>
<div class="line"><a id="l01019" name="l01019"></a><span class="lineno"> 1019</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01020" name="l01020"></a><span class="lineno"> 1020</span><span class="comment">   * The internally stored integer representation of the `enum` value passed to the 1-arg constructor; meaningless</span></div>
<div class="line"><a id="l01021" name="l01021"></a><span class="lineno"> 1021</span><span class="comment">   * and ignored if 0-arg ctor was used (empty() is `true`).</span></div>
<div class="line"><a id="l01022" name="l01022"></a><span class="lineno"> 1022</span><span class="comment">   */</span></div>
<div class="line"><a id="l01023" name="l01023"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Component.html#a5be216ad60f3e344a22151bdf4d8d8b6"> 1023</a></span>  <a class="code hl_typedef" href="classflow_1_1log_1_1Component.html#a287888e2943b312f4febc3e8e130fc80">enum_raw_t</a> <a class="code hl_variable" href="classflow_1_1log_1_1Component.html#a5be216ad60f3e344a22151bdf4d8d8b6">m_payload_enum_raw_value</a>;</div>
<div class="line"><a id="l01024" name="l01024"></a><span class="lineno"> 1024</span>}; <span class="comment">// class Component</span></div>
<div class="line"><a id="l01025" name="l01025"></a><span class="lineno"> 1025</span><span class="comment"></span> </div>
<div class="line"><a id="l01026" name="l01026"></a><span class="lineno"> 1026</span><span class="comment">/**</span></div>
<div class="line"><a id="l01027" name="l01027"></a><span class="lineno"> 1027</span><span class="comment"> * Simple data store containing all of the information generated at every logging call site by flow::log, except</span></div>
<div class="line"><a id="l01028" name="l01028"></a><span class="lineno"> 1028</span><span class="comment"> * the message itself, which is passed to Logger::do_log() assuming Logger::should_log() had returned `true`.</span></div>
<div class="line"><a id="l01029" name="l01029"></a><span class="lineno"> 1029</span><span class="comment"> * User only need to worry about this when dealing with the internals of a Logger implementation.  Copying is to be</span></div>
<div class="line"><a id="l01030" name="l01030"></a><span class="lineno"> 1030</span><span class="comment"> * avoided, as there are some non-trivial data stored here; though it is not too bad.</span></div>
<div class="line"><a id="l01031" name="l01031"></a><span class="lineno"> 1031</span><span class="comment"> *</span></div>
<div class="line"><a id="l01032" name="l01032"></a><span class="lineno"> 1032</span><span class="comment"> * @warning If changing the insides of Msg_metadata, ensure free function `deep_copy(const Msg_metadata&amp;)`</span></div>
<div class="line"><a id="l01033" name="l01033"></a><span class="lineno"> 1033</span><span class="comment"> *          remains accurate.</span></div>
<div class="line"><a id="l01034" name="l01034"></a><span class="lineno"> 1034</span><span class="comment"> *</span></div>
<div class="line"><a id="l01035" name="l01035"></a><span class="lineno"> 1035</span><span class="comment"> * @todo Add support in Msg_metadata for a message ID which could more straightforwardly help the human log reader</span></div>
<div class="line"><a id="l01036" name="l01036"></a><span class="lineno"> 1036</span><span class="comment"> * to map a log line to the originating log call site in source code.  One approach, then, might be to output</span></div>
<div class="line"><a id="l01037" name="l01037"></a><span class="lineno"> 1037</span><span class="comment"> * that message ID when available; else output #m_msg_src_file, #m_msg_src_line, #m_msg_src_function; or maybe</span></div>
<div class="line"><a id="l01038" name="l01038"></a><span class="lineno"> 1038</span><span class="comment"> * both.</span></div>
<div class="line"><a id="l01039" name="l01039"></a><span class="lineno"> 1039</span><span class="comment"> */</span></div>
<div class="line"><a id="l01040" name="l01040"></a><span class="lineno"><a class="line" href="structflow_1_1log_1_1Msg__metadata.html"> 1040</a></span><span class="keyword">struct </span><a class="code hl_struct" href="structflow_1_1log_1_1Msg__metadata.html">Msg_metadata</a></div>
<div class="line"><a id="l01041" name="l01041"></a><span class="lineno"> 1041</span>{</div>
<div class="line"><a id="l01042" name="l01042"></a><span class="lineno"> 1042</span>  <span class="comment">// Data.</span></div>
<div class="line"><a id="l01043" name="l01043"></a><span class="lineno"> 1043</span><span class="comment"></span> </div>
<div class="line"><a id="l01044" name="l01044"></a><span class="lineno"> 1044</span><span class="comment">  /// Component of message, as of this writing coming from either Log_context constructor or FLOW_LOG_SET_CONTEXT().</span></div>
<div class="line"><a id="l01045" name="l01045"></a><span class="lineno"><a class="line" href="structflow_1_1log_1_1Msg__metadata.html#a9d966ba8a227d1e7af587a8191ccf934"> 1045</a></span><span class="comment"></span>  <a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a> <a class="code hl_variable" href="structflow_1_1log_1_1Msg__metadata.html#a9d966ba8a227d1e7af587a8191ccf934">m_msg_component</a>;</div>
<div class="line"><a id="l01046" name="l01046"></a><span class="lineno"> 1046</span><span class="comment"></span> </div>
<div class="line"><a id="l01047" name="l01047"></a><span class="lineno"> 1047</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01048" name="l01048"></a><span class="lineno"> 1048</span><span class="comment">   * Severity of message, typically determined by choice of macro (e.g., FLOW_LOG_WARNING() vs. FLOW_LOG_INFO()) at the</span></div>
<div class="line"><a id="l01049" name="l01049"></a><span class="lineno"> 1049</span><span class="comment">   * call site; though it can also be supplied manually via `FLOW_LOG_WITH[OUT]_CHECKING()` macro arg.</span></div>
<div class="line"><a id="l01050" name="l01050"></a><span class="lineno"> 1050</span><span class="comment">   */</span></div>
<div class="line"><a id="l01051" name="l01051"></a><span class="lineno"><a class="line" href="structflow_1_1log_1_1Msg__metadata.html#a38ed0fc480839dd1c177fa5a8d59368a"> 1051</a></span>  <a class="code hl_enumeration" href="namespaceflow_1_1log.html#a5c602384e6fe9d7642740ac2fae4ad04">Sev</a> <a class="code hl_variable" href="structflow_1_1log_1_1Msg__metadata.html#a38ed0fc480839dd1c177fa5a8d59368a">m_msg_sev</a>;</div>
<div class="line"><a id="l01052" name="l01052"></a><span class="lineno"> 1052</span><span class="comment"></span> </div>
<div class="line"><a id="l01053" name="l01053"></a><span class="lineno"> 1053</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01054" name="l01054"></a><span class="lineno"> 1054</span><span class="comment">   * Pointer/length into static-storage string that would have come from built-in `__FILE__` macro which is</span></div>
<div class="line"><a id="l01055" name="l01055"></a><span class="lineno"> 1055</span><span class="comment">   * auto-invoked by all `FLOW_LOG_*()` logging call sites.  Formally this should be the pointer/length representing</span></div>
<div class="line"><a id="l01056" name="l01056"></a><span class="lineno"> 1056</span><span class="comment">   * the substring of `__FILE__` that you wish to be logged in its entirely, no more and no less.  For example</span></div>
<div class="line"><a id="l01057" name="l01057"></a><span class="lineno"> 1057</span><span class="comment">   * the pointer might be to the first character, the lengh equal to `strlen()`; or more practically it might be</span></div>
<div class="line"><a id="l01058" name="l01058"></a><span class="lineno"> 1058</span><span class="comment">   * one past the right-most dir separator character (and the length decremented accordingly).</span></div>
<div class="line"><a id="l01059" name="l01059"></a><span class="lineno"> 1059</span><span class="comment">   *</span></div>
<div class="line"><a id="l01060" name="l01060"></a><span class="lineno"> 1060</span><span class="comment">   * To be explicit: The underlying memory must never be deallocated, in that it should never have been allocated on the</span></div>
<div class="line"><a id="l01061" name="l01061"></a><span class="lineno"> 1061</span><span class="comment">   * heap but in static storage.</span></div>
<div class="line"><a id="l01062" name="l01062"></a><span class="lineno"> 1062</span><span class="comment">   *</span></div>
<div class="line"><a id="l01063" name="l01063"></a><span class="lineno"> 1063</span><span class="comment">   * ### Perf notes ###</span></div>
<div class="line"><a id="l01064" name="l01064"></a><span class="lineno"> 1064</span><span class="comment">   * We store a util::String_view, not a `const char*`, which means not only a pointer but a length is stored here</span></div>
<div class="line"><a id="l01065" name="l01065"></a><span class="lineno"> 1065</span><span class="comment">   * internally.  That&#39;s fine (we discuss trade-offs just below); it should barely affect the perf of copying</span></div>
<div class="line"><a id="l01066" name="l01066"></a><span class="lineno"> 1066</span><span class="comment">   * Msg_metadata.  However the length must be initialized.  To initialize it in the most optimized way, recognize</span></div>
<div class="line"><a id="l01067" name="l01067"></a><span class="lineno"> 1067</span><span class="comment">   * that it will come from `__FILE__` which is really a string literal substituted by preprocessor; therefore</span></div>
<div class="line"><a id="l01068" name="l01068"></a><span class="lineno"> 1068</span><span class="comment">   * the length can be obtained at compile time via `sizeof()`.  Hence use the 2-arg `String_view` ctor which takes</span></div>
<div class="line"><a id="l01069" name="l01069"></a><span class="lineno"> 1069</span><span class="comment">   * the pointer *and* the length instead of figuring the latter out via `strlen()` which is linear-time.</span></div>
<div class="line"><a id="l01070" name="l01070"></a><span class="lineno"> 1070</span><span class="comment">   * Update: The util::String_view in use as of this writing declares the 1-arg ctor as `constexpr` which indicates</span></div>
<div class="line"><a id="l01071" name="l01071"></a><span class="lineno"> 1071</span><span class="comment">   * it might be able to do the `strlen()` (or equivalent) at compile-time.  Nevertheless, this feels (and I say this</span></div>
<div class="line"><a id="l01072" name="l01072"></a><span class="lineno"> 1072</span><span class="comment">   * with some related experience) like something that may or may not actually be implemented by a given compiler.</span></div>
<div class="line"><a id="l01073" name="l01073"></a><span class="lineno"> 1073</span><span class="comment">   * So it&#39;s probably safer (in terms of portability) to still follow the 2-arg ctor advice above.</span></div>
<div class="line"><a id="l01074" name="l01074"></a><span class="lineno"> 1074</span><span class="comment">   *</span></div>
<div class="line"><a id="l01075" name="l01075"></a><span class="lineno"> 1075</span><span class="comment">   * If it is desired (as suggested in an example above) to represent a mere substring of that, then as long as</span></div>
<div class="line"><a id="l01076" name="l01076"></a><span class="lineno"> 1076</span><span class="comment">   * the computation of the appropriate first character past index 0 satisfies `constexpr` requirements (meaning, it</span></div>
<div class="line"><a id="l01077" name="l01077"></a><span class="lineno"> 1077</span><span class="comment">   * will be computed at compile time, not runtime) -- as does the according decrement of the length -- then you&#39;re</span></div>
<div class="line"><a id="l01078" name="l01078"></a><span class="lineno"> 1078</span><span class="comment">   * still fine.  If it is done at runtime, then that&#39;s a hit to perf, so avoid it if at all possible.</span></div>
<div class="line"><a id="l01079" name="l01079"></a><span class="lineno"> 1079</span><span class="comment">   *</span></div>
<div class="line"><a id="l01080" name="l01080"></a><span class="lineno"> 1080</span><span class="comment">   * If indeed you do want ultimately to output a substring of `__FILE__`, then in order to guarantee or at least</span></div>
<div class="line"><a id="l01081" name="l01081"></a><span class="lineno"> 1081</span><span class="comment">   * increase the chance of compile-time computation of that substring you should in fact do it as early as possible</span></div>
<div class="line"><a id="l01082" name="l01082"></a><span class="lineno"> 1082</span><span class="comment">   * at the log call site as opposed to later/nearer the time of final output to device/whatever by Logger.  In other</span></div>
<div class="line"><a id="l01083" name="l01083"></a><span class="lineno"> 1083</span><span class="comment">   * words in that case do try to set this value to the substring from the start; don&#39;t leave it to the Logger.</span></div>
<div class="line"><a id="l01084" name="l01084"></a><span class="lineno"> 1084</span><span class="comment">   *</span></div>
<div class="line"><a id="l01085" name="l01085"></a><span class="lineno"> 1085</span><span class="comment">   * ### Perf rationale: Why not use `const char*` instead? ###</span></div>
<div class="line"><a id="l01086" name="l01086"></a><span class="lineno"> 1086</span><span class="comment">   * (This is arguably very nitpicky anyway, but these objects are generated and passed around at every single log call</span></div>
<div class="line"><a id="l01087" name="l01087"></a><span class="lineno"> 1087</span><span class="comment">   * site, so we should try to save every little bit.)  Let&#39;s stipulate that the cost of storing (RAM; and copying)</span></div>
<div class="line"><a id="l01088" name="l01088"></a><span class="lineno"> 1088</span><span class="comment">   * the length is negligible.  The next concern is initializing the length; the above shows that&#39;s free in practice.</span></div>
<div class="line"><a id="l01089" name="l01089"></a><span class="lineno"> 1089</span><span class="comment">   * Finally, when output to the final device/whatever occurs within Logger impl, there are two possibilities of how</span></div>
<div class="line"><a id="l01090" name="l01090"></a><span class="lineno"> 1090</span><span class="comment">   * it might realistically act.  One, it might search for the NUL char anyway -- in which case we&#39;ve changed nothing</span></div>
<div class="line"><a id="l01091" name="l01091"></a><span class="lineno"> 1091</span><span class="comment">   * perf-wise -- as it copies for output purposes.  Two, it might require the length of the string and hence use</span></div>
<div class="line"><a id="l01092" name="l01092"></a><span class="lineno"> 1092</span><span class="comment">   * `String_view::size()` and then perform the copy; in that case we have saved a linear search.  (For example, if</span></div>
<div class="line"><a id="l01093" name="l01093"></a><span class="lineno"> 1093</span><span class="comment">   * the Logger is printing to an `ostream`, then there exists an `operator&lt;&lt;(ostream, String_view)` that&#39;d be</span></div>
<div class="line"><a id="l01094" name="l01094"></a><span class="lineno"> 1094</span><span class="comment">   * automatically used and would of course use the saved length properly.)  So, it&#39;s a win or at worst a tie.</span></div>
<div class="line"><a id="l01095" name="l01095"></a><span class="lineno"> 1095</span><span class="comment">   */</span></div>
<div class="line"><a id="l01096" name="l01096"></a><span class="lineno"><a class="line" href="structflow_1_1log_1_1Msg__metadata.html#a5e7224fd18f1b9b2600508ac399687dd"> 1096</a></span>  <a class="code hl_typedef" href="namespaceflow_1_1util.html#ae4dc52186797094b3040379ff19124c9">util::String_view</a> <a class="code hl_variable" href="structflow_1_1log_1_1Msg__metadata.html#a5e7224fd18f1b9b2600508ac399687dd">m_msg_src_file</a>;</div>
<div class="line"><a id="l01097" name="l01097"></a><span class="lineno"> 1097</span><span class="comment"></span> </div>
<div class="line"><a id="l01098" name="l01098"></a><span class="lineno"> 1098</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01099" name="l01099"></a><span class="lineno"> 1099</span><span class="comment">   * Copy of integer that would have come from built-in `__LINE__` macro which is auto-invoked by all `FLOW_LOG_*()`</span></div>
<div class="line"><a id="l01100" name="l01100"></a><span class="lineno"> 1100</span><span class="comment">   * logging call sites.</span></div>
<div class="line"><a id="l01101" name="l01101"></a><span class="lineno"> 1101</span><span class="comment">   */</span></div>
<div class="line"><a id="l01102" name="l01102"></a><span class="lineno"><a class="line" href="structflow_1_1log_1_1Msg__metadata.html#a2f17801fae328d1fdc070edc2578dd91"> 1102</a></span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> <a class="code hl_variable" href="structflow_1_1log_1_1Msg__metadata.html#a2f17801fae328d1fdc070edc2578dd91">m_msg_src_line</a>;</div>
<div class="line"><a id="l01103" name="l01103"></a><span class="lineno"> 1103</span><span class="comment"></span> </div>
<div class="line"><a id="l01104" name="l01104"></a><span class="lineno"> 1104</span><span class="comment">  /// Analogous to #m_msg_src_file but coming from `__FUNCTION__`, not `__FILE__`.  See #m_msg_src_file perf notes.</span></div>
<div class="line"><a id="l01105" name="l01105"></a><span class="lineno"><a class="line" href="structflow_1_1log_1_1Msg__metadata.html#af7704a632434e7b52c43ab6047cf023b"> 1105</a></span><span class="comment"></span>  <a class="code hl_typedef" href="namespaceflow_1_1util.html#ae4dc52186797094b3040379ff19124c9">util::String_view</a> <a class="code hl_variable" href="structflow_1_1log_1_1Msg__metadata.html#af7704a632434e7b52c43ab6047cf023b">m_msg_src_function</a>;</div>
<div class="line"><a id="l01106" name="l01106"></a><span class="lineno"> 1106</span><span class="comment"></span> </div>
<div class="line"><a id="l01107" name="l01107"></a><span class="lineno"> 1107</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01108" name="l01108"></a><span class="lineno"> 1108</span><span class="comment">   * Time stamp from as close as possible to entry into the log call site (usually `FLOW_LOG_WARNING()` or similar).</span></div>
<div class="line"><a id="l01109" name="l01109"></a><span class="lineno"> 1109</span><span class="comment">   *</span></div>
<div class="line"><a id="l01110" name="l01110"></a><span class="lineno"> 1110</span><span class="comment">   * `std::chrono` is used instead of boost.chrono for certain internal output reasons in Ostream_log_msg_writer.</span></div>
<div class="line"><a id="l01111" name="l01111"></a><span class="lineno"> 1111</span><span class="comment">   */</span></div>
<div class="line"><a id="l01112" name="l01112"></a><span class="lineno"><a class="line" href="structflow_1_1log_1_1Msg__metadata.html#a11e04fcee8409b76adb9aaa3108f90e1"> 1112</a></span>  std::chrono::system_clock::time_point <a class="code hl_variable" href="structflow_1_1log_1_1Msg__metadata.html#a11e04fcee8409b76adb9aaa3108f90e1">m_called_when</a>;</div>
<div class="line"><a id="l01113" name="l01113"></a><span class="lineno"> 1113</span><span class="comment"></span> </div>
<div class="line"><a id="l01114" name="l01114"></a><span class="lineno"> 1114</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01115" name="l01115"></a><span class="lineno"> 1115</span><span class="comment">   * Thread nickname, as for Logger::this_thread_set_logged_nickname(), of the thread from which the</span></div>
<div class="line"><a id="l01116" name="l01116"></a><span class="lineno"> 1116</span><span class="comment">   * log call was invoked; or an empty string if the thread had no such nickname set at the time.</span></div>
<div class="line"><a id="l01117" name="l01117"></a><span class="lineno"> 1117</span><span class="comment">   *</span></div>
<div class="line"><a id="l01118" name="l01118"></a><span class="lineno"> 1118</span><span class="comment">   * @see #m_call_thread_id</span></div>
<div class="line"><a id="l01119" name="l01119"></a><span class="lineno"> 1119</span><span class="comment">   *</span></div>
<div class="line"><a id="l01120" name="l01120"></a><span class="lineno"> 1120</span><span class="comment">   * ### Perf note ###</span></div>
<div class="line"><a id="l01121" name="l01121"></a><span class="lineno"> 1121</span><span class="comment">   * Setting this involves an `std::string` copy; the cost of this is worth considering given that this is done</span></div>
<div class="line"><a id="l01122" name="l01122"></a><span class="lineno"> 1122</span><span class="comment">   * for every single log call site, if the nickname is indeed set.  See performance note in doc header of</span></div>
<div class="line"><a id="l01123" name="l01123"></a><span class="lineno"> 1123</span><span class="comment">   * Logger::this_thread_set_logged_nickname() for the recommendation and details.  (Long story short, if you keep</span></div>
<div class="line"><a id="l01124" name="l01124"></a><span class="lineno"> 1124</span><span class="comment">   * it at N `char`s or fewer, the cost of a non-empty #m_call_thread_nickname becomes equal to that of an</span></div>
<div class="line"><a id="l01125" name="l01125"></a><span class="lineno"> 1125</span><span class="comment">   * empty one.  N might be 15 in gcc 5.)</span></div>
<div class="line"><a id="l01126" name="l01126"></a><span class="lineno"> 1126</span><span class="comment">   */</span></div>
<div class="line"><a id="l01127" name="l01127"></a><span class="lineno"><a class="line" href="structflow_1_1log_1_1Msg__metadata.html#a4588cf8c827944e5379c6ad1fd11d6db"> 1127</a></span>  std::string <a class="code hl_variable" href="structflow_1_1log_1_1Msg__metadata.html#a4588cf8c827944e5379c6ad1fd11d6db">m_call_thread_nickname</a>;</div>
<div class="line"><a id="l01128" name="l01128"></a><span class="lineno"> 1128</span><span class="comment"></span> </div>
<div class="line"><a id="l01129" name="l01129"></a><span class="lineno"> 1129</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01130" name="l01130"></a><span class="lineno"> 1130</span><span class="comment">   * Thread ID of the thread from which the log call was invoked; or a default-constructed (no-thread) such</span></div>
<div class="line"><a id="l01131" name="l01131"></a><span class="lineno"> 1131</span><span class="comment">   * thread ID if the thread has a nickname, meaning `!m_call_thread_nickname.empty()`.  The working assumption is</span></div>
<div class="line"><a id="l01132" name="l01132"></a><span class="lineno"> 1132</span><span class="comment">   * that (1) both members are met for direct log output only and no other logic; and (2) the nickname is preferable</span></div>
<div class="line"><a id="l01133" name="l01133"></a><span class="lineno"> 1133</span><span class="comment">   * when set, the thread ID being the fallback.  (If this sounds meh, consider that it&#39;s entirely reasonable to make</span></div>
<div class="line"><a id="l01134" name="l01134"></a><span class="lineno"> 1134</span><span class="comment">   * the nickname contain some nice info *and* the original thread ID as well in string form.  However, mind</span></div>
<div class="line"><a id="l01135" name="l01135"></a><span class="lineno"> 1135</span><span class="comment">   * the length -- the Performance Note in #m_call_thread_nickname doc header.)</span></div>
<div class="line"><a id="l01136" name="l01136"></a><span class="lineno"> 1136</span><span class="comment">   */</span></div>
<div class="line"><a id="l01137" name="l01137"></a><span class="lineno"><a class="line" href="structflow_1_1log_1_1Msg__metadata.html#a278ef30d1bdceb9482c0aef097177c91"> 1137</a></span>  <a class="code hl_typedef" href="namespaceflow_1_1util.html#a0a4e7b2d3107bd630e0dc0c0b8f2e4de">util::Thread_id</a> <a class="code hl_variable" href="structflow_1_1log_1_1Msg__metadata.html#a278ef30d1bdceb9482c0aef097177c91">m_call_thread_id</a>;</div>
<div class="line"><a id="l01138" name="l01138"></a><span class="lineno"> 1138</span>}; <span class="comment">// struct Msg_metadata</span></div>
<div class="line"><a id="l01139" name="l01139"></a><span class="lineno"> 1139</span><span class="comment"></span> </div>
<div class="line"><a id="l01140" name="l01140"></a><span class="lineno"> 1140</span><span class="comment">/**</span></div>
<div class="line"><a id="l01141" name="l01141"></a><span class="lineno"> 1141</span><span class="comment"> * Interface that the user should implement, passing the implementing Logger into logging classes</span></div>
<div class="line"><a id="l01142" name="l01142"></a><span class="lineno"> 1142</span><span class="comment"> * (Flow&#39;s own classes like net_flow::Node; and user&#39;s own logging classes) at construction (plus free/`static`</span></div>
<div class="line"><a id="l01143" name="l01143"></a><span class="lineno"> 1143</span><span class="comment"> * logging functions).  The class (or function) will then implicitly</span></div>
<div class="line"><a id="l01144" name="l01144"></a><span class="lineno"> 1144</span><span class="comment"> * use that Logger in the logging apparatus (such as `FLOW_LOG_...()` macros) to log messages</span></div>
<div class="line"><a id="l01145" name="l01145"></a><span class="lineno"> 1145</span><span class="comment"> * into the user&#39;s preferred logging output(s).  One can think of the class implementing this interface</span></div>
<div class="line"><a id="l01146" name="l01146"></a><span class="lineno"> 1146</span><span class="comment"> * as the glue between Flow logging and either the user&#39;s lower-level logging system or some output device</span></div>
<div class="line"><a id="l01147" name="l01147"></a><span class="lineno"> 1147</span><span class="comment"> * (like console, files) directly.</span></div>
<div class="line"><a id="l01148" name="l01148"></a><span class="lineno"> 1148</span><span class="comment"> *</span></div>
<div class="line"><a id="l01149" name="l01149"></a><span class="lineno"> 1149</span><span class="comment"> * The reason should_log() and do_log() are decoupled like this is for a fast</span></div>
<div class="line"><a id="l01150" name="l01150"></a><span class="lineno"> 1150</span><span class="comment"> * implementation of the `FLOW_LOG_...()` macros (see FLOW_LOG_WITH_CHECKING() in particular).</span></div>
<div class="line"><a id="l01151" name="l01151"></a><span class="lineno"> 1151</span><span class="comment"> *</span></div>
<div class="line"><a id="l01152" name="l01152"></a><span class="lineno"> 1152</span><span class="comment"> * There is also a small set of app-wide (`static`) utilities, including the ability to nickname any</span></div>
<div class="line"><a id="l01153" name="l01153"></a><span class="lineno"> 1153</span><span class="comment"> * given thread, which causes that nickname (instead of the thread ID) to be logged in subsequent log</span></div>
<div class="line"><a id="l01154" name="l01154"></a><span class="lineno"> 1154</span><span class="comment"> * messages.</span></div>
<div class="line"><a id="l01155" name="l01155"></a><span class="lineno"> 1155</span><span class="comment"> *</span></div>
<div class="line"><a id="l01156" name="l01156"></a><span class="lineno"> 1156</span><span class="comment"> * ### Stream continuity (and threads) ###</span></div>
<div class="line"><a id="l01157" name="l01157"></a><span class="lineno"> 1157</span><span class="comment"> * As slightly advanced `ostream` users know, an `ostream` carries state that can be set via explicit method</span></div>
<div class="line"><a id="l01158" name="l01158"></a><span class="lineno"> 1158</span><span class="comment"> * calls such as `ostream::setf()` and via &quot;printing&quot; manipulators such as `std::hex` to a given `ostream`.</span></div>
<div class="line"><a id="l01159" name="l01159"></a><span class="lineno"> 1159</span><span class="comment"> * Regular values printed to `ostream` will come out differently depending on the current state (e.g., `&lt;&lt; 14` may</span></div>
<div class="line"><a id="l01160" name="l01160"></a><span class="lineno"> 1160</span><span class="comment"> * show up as a decimal or a hex integer depending on preceding formatters).  If you use these state-affecting features,</span></div>
<div class="line"><a id="l01161" name="l01161"></a><span class="lineno"> 1161</span><span class="comment"> * be aware of the following semantics:</span></div>
<div class="line"><a id="l01162" name="l01162"></a><span class="lineno"> 1162</span><span class="comment"> *</span></div>
<div class="line"><a id="l01163" name="l01163"></a><span class="lineno"> 1163</span><span class="comment"> * - The system works as if there is exactly one `ostream` for every distinct combination (`logger`, T), where:</span></div>
<div class="line"><a id="l01164" name="l01164"></a><span class="lineno"> 1164</span><span class="comment"> *   - `logger` is a distinct Logger object, as identified by the address in its `Logger::this` pointer.</span></div>
<div class="line"><a id="l01165" name="l01165"></a><span class="lineno"> 1165</span><span class="comment"> *   - T is a distinct thread such that the API user has previously, at least once, invoked a logging API that works</span></div>
<div class="line"><a id="l01166" name="l01166"></a><span class="lineno"> 1166</span><span class="comment"> *     with Logger `ostream`s -- from that thread.  (The APIs that qualify are essentially various APIs that actually</span></div>
<div class="line"><a id="l01167" name="l01167"></a><span class="lineno"> 1167</span><span class="comment"> *     log messages or attempt to set formatting for subsequent messages or are used to subsequently do either.)</span></div>
<div class="line"><a id="l01168" name="l01168"></a><span class="lineno"> 1168</span><span class="comment"> * - One can think of a given (`logger`, T) combo&#39;s `ostream` as being created on-demand the first time a given</span></div>
<div class="line"><a id="l01169" name="l01169"></a><span class="lineno"> 1169</span><span class="comment"> *   Logger `logger` attempts to do something logging-related from a given thread T.  Subsequently, with that combo</span></div>
<div class="line"><a id="l01170" name="l01170"></a><span class="lineno"> 1170</span><span class="comment"> *   used again and again, the stream is internally looked up with high performance.  The on-demand creation is slower</span></div>
<div class="line"><a id="l01171" name="l01171"></a><span class="lineno"> 1171</span><span class="comment"> *   but relatively rare given the low expected count of threads and `Logger`s.</span></div>
<div class="line"><a id="l01172" name="l01172"></a><span class="lineno"> 1172</span><span class="comment"> * - Any stream state change carried by a user API call for a given distinct (as defined above) stream S:</span></div>
<div class="line"><a id="l01173" name="l01173"></a><span class="lineno"> 1173</span><span class="comment"> *   - *will* persistently affect the subsequent output of any subsequent log message payload on stream S,</span></div>
<div class="line"><a id="l01174" name="l01174"></a><span class="lineno"> 1174</span><span class="comment"> *     including the same log message following the given state change, and including any subsequent log messages;</span></div>
<div class="line"><a id="l01175" name="l01175"></a><span class="lineno"> 1175</span><span class="comment"> *   - *will not* affect any stream other than S;</span></div>
<div class="line"><a id="l01176" name="l01176"></a><span class="lineno"> 1176</span><span class="comment"> *   - *will not* affect any intra-message prefixes or suffixes (such as originating file, function, line that may</span></div>
<div class="line"><a id="l01177" name="l01177"></a><span class="lineno"> 1177</span><span class="comment"> *     be inserted before every log message automatically) added by the Logger API implementation.</span></div>
<div class="line"><a id="l01178" name="l01178"></a><span class="lineno"> 1178</span><span class="comment"> * - There are essentially two ways to affect state of stream S.  Either one must be invoked from the thread T</span></div>
<div class="line"><a id="l01179" name="l01179"></a><span class="lineno"> 1179</span><span class="comment"> *   pertaining to stream S, and the Logger object involved must also be the one pertaining to S.</span></div>
<div class="line"><a id="l01180" name="l01180"></a><span class="lineno"> 1180</span><span class="comment"> *   - The state change may be part of the sequence of `operator&lt;&lt;()` operands passed to a logging API.</span></div>
<div class="line"><a id="l01181" name="l01181"></a><span class="lineno"> 1181</span><span class="comment"> *     However, note that for it to take effect, it must not be filtered out by a Sev filter check (basically,</span></div>
<div class="line"><a id="l01182" name="l01182"></a><span class="lineno"> 1182</span><span class="comment"> *     the containing log message must actually end up in the log, not filtered away).</span></div>
<div class="line"><a id="l01183" name="l01183"></a><span class="lineno"> 1183</span><span class="comment"> *     - In this case, the state change must be via a manipulator formatter like `std::setfill`, `std::hex`,</span></div>
<div class="line"><a id="l01184" name="l01184"></a><span class="lineno"> 1184</span><span class="comment"> *       `boost::chrono::seconds`, etc.</span></div>
<div class="line"><a id="l01185" name="l01185"></a><span class="lineno"> 1185</span><span class="comment"> *   - The state change may be a direct call invoked on a given `ostream S`, where to get access to `S` one would</span></div>
<div class="line"><a id="l01186" name="l01186"></a><span class="lineno"> 1186</span><span class="comment"> *     call Logger::this_thread_ostream() to receive the pointer `&amp;S&#39;, for the current thread and</span></div>
<div class="line"><a id="l01187" name="l01187"></a><span class="lineno"> 1187</span><span class="comment"> *     the Logger on which the method is executed.  Once you have `S`, you may call state manipulators such as</span></div>
<div class="line"><a id="l01188" name="l01188"></a><span class="lineno"> 1188</span><span class="comment"> *     `S.setf();` or, again, manipulators via `S &lt;&lt; std::hex;` and similar.</span></div>
<div class="line"><a id="l01189" name="l01189"></a><span class="lineno"> 1189</span><span class="comment"> *     - Using this_thread_ostream() for any purpose other than to change stream state (i.e., to output actual</span></div>
<div class="line"><a id="l01190" name="l01190"></a><span class="lineno"> 1190</span><span class="comment"> *       characters, like `S &lt;&lt; &quot;Hello, world!&quot;;`) will result in undefined behavior.  Do not.  Use logging APIs for</span></div>
<div class="line"><a id="l01191" name="l01191"></a><span class="lineno"> 1191</span><span class="comment"> *       that.</span></div>
<div class="line"><a id="l01192" name="l01192"></a><span class="lineno"> 1192</span><span class="comment"> * - Even if the Logger implementation uses `ostream` for ultimate output of characters (and it absolutely does not</span></div>
<div class="line"><a id="l01193" name="l01193"></a><span class="lineno"> 1193</span><span class="comment"> *   have to do any such thing), that `ostream` is totally orthogonal and irrelevant to the one being discussed here.</span></div>
<div class="line"><a id="l01194" name="l01194"></a><span class="lineno"> 1194</span><span class="comment"> *   E.g., Simple_ostream_logger may print to `std::cout`, but the formatters we are discussing affect a totally</span></div>
<div class="line"><a id="l01195" name="l01195"></a><span class="lineno"> 1195</span><span class="comment"> *   different, internal stream, not that `std::cout`.  In fact, the internal stream is in memory, not</span></div>
<div class="line"><a id="l01196" name="l01196"></a><span class="lineno"> 1196</span><span class="comment"> *   file/console/whatever.  I point this out only to avoid confusion.</span></div>
<div class="line"><a id="l01197" name="l01197"></a><span class="lineno"> 1197</span><span class="comment"> *</span></div>
<div class="line"><a id="l01198" name="l01198"></a><span class="lineno"> 1198</span><span class="comment"> * ### Basic suggested strategy for implementing a Logger ###</span></div>
<div class="line"><a id="l01199" name="l01199"></a><span class="lineno"> 1199</span><span class="comment"> * The simplicity of the Logger interface, and the lack of mandatory rigidity in how one might configure it</span></div>
<div class="line"><a id="l01200" name="l01200"></a><span class="lineno"> 1200</span><span class="comment"> * (particularly w/r/t per-`Component` verbosity and output format), assures the sky is the limit for how one</span></div>
<div class="line"><a id="l01201" name="l01201"></a><span class="lineno"> 1201</span><span class="comment"> * implements their own custom Logger.  However, in the absence of great reasons not to, we suggest one follows</span></div>
<div class="line"><a id="l01202" name="l01202"></a><span class="lineno"> 1202</span><span class="comment"> * the lead of out-of-the-box existing `Logger`s in Flow, which adds a degree of rigidity as to the implementation</span></div>
<div class="line"><a id="l01203" name="l01203"></a><span class="lineno"> 1203</span><span class="comment"> * but also seems to provide all the features seemingly commonly desired in practice.  Namely, like</span></div>
<div class="line"><a id="l01204" name="l01204"></a><span class="lineno"> 1204</span><span class="comment"> * (say) Simple_ostream_logger, Buffer_logger, and Async_file_logger, do this:</span></div>
<div class="line"><a id="l01205" name="l01205"></a><span class="lineno"> 1205</span><span class="comment"> *   - Take a Config pointer at constructor and save it (do not copy the Config).  (There are thread safety</span></div>
<div class="line"><a id="l01206" name="l01206"></a><span class="lineno"> 1206</span><span class="comment"> *     implications.)</span></div>
<div class="line"><a id="l01207" name="l01207"></a><span class="lineno"> 1207</span><span class="comment"> *   - Internally use some kind of `ostream`-subclass member to a target device, if at all possible.</span></div>
<div class="line"><a id="l01208" name="l01208"></a><span class="lineno"> 1208</span><span class="comment"> *     (boost.asio will let you even write to network this way; but at least console output, file output, and</span></div>
<div class="line"><a id="l01209" name="l01209"></a><span class="lineno"> 1209</span><span class="comment"> *     memory string output are 100% practical via `ostream`s.  Existing `Logger`s provide examples.)</span></div>
<div class="line"><a id="l01210" name="l01210"></a><span class="lineno"> 1210</span><span class="comment"> *   - Internally use an Ostream_log_msg_writer to write to said `ostream`, the formatting thereof being configurable</span></div>
<div class="line"><a id="l01211" name="l01211"></a><span class="lineno"> 1211</span><span class="comment"> *     in a uniform way via the saved Config.</span></div>
<div class="line"><a id="l01212" name="l01212"></a><span class="lineno"> 1212</span><span class="comment"> *   - Forward should_log() logic to the saved Config (Config::output_whether_should_log()), so that verbosity is</span></div>
<div class="line"><a id="l01213" name="l01213"></a><span class="lineno"> 1213</span><span class="comment"> *     flexibly but uniformly set via Config.</span></div>
<div class="line"><a id="l01214" name="l01214"></a><span class="lineno"> 1214</span><span class="comment"> *   - It is up to the user, now, to set up the Config appropriately when passing it to your `Logger` subclass</span></div>
<div class="line"><a id="l01215" name="l01215"></a><span class="lineno"> 1215</span><span class="comment"> *     constructor.  The user would simply follow the documentation for Config, and you need neither re-implement</span></div>
<div class="line"><a id="l01216" name="l01216"></a><span class="lineno"> 1216</span><span class="comment"> *     nor re-document configurability of your Logger.</span></div>
<div class="line"><a id="l01217" name="l01217"></a><span class="lineno"> 1217</span><span class="comment"> *</span></div>
<div class="line"><a id="l01218" name="l01218"></a><span class="lineno"> 1218</span><span class="comment"> * Reminder: Config and Ostream_log_msg_writer are optional to use, and one can use one, both, or neither (though</span></div>
<div class="line"><a id="l01219" name="l01219"></a><span class="lineno"> 1219</span><span class="comment"> * the latter itself does expect one of the former; of course you can just load up your own new Config, in case</span></div>
<div class="line"><a id="l01220" name="l01220"></a><span class="lineno"> 1220</span><span class="comment"> * you don&#39;t want to use a user Config taken via your constructor API).  However, unless there&#39;s something insufficient</span></div>
<div class="line"><a id="l01221" name="l01221"></a><span class="lineno"> 1221</span><span class="comment"> * about them, various benefits abound in using both.  Furthermore, if something is lacking, consider extending that</span></div>
<div class="line"><a id="l01222" name="l01222"></a><span class="lineno"> 1222</span><span class="comment"> * system to the benefit of all/most other `Logger`s as opposed to throwing it away and re-implementing something new</span></div>
<div class="line"><a id="l01223" name="l01223"></a><span class="lineno"> 1223</span><span class="comment"> * for just your new Logger.</span></div>
<div class="line"><a id="l01224" name="l01224"></a><span class="lineno"> 1224</span><span class="comment"> *</span></div>
<div class="line"><a id="l01225" name="l01225"></a><span class="lineno"> 1225</span><span class="comment"> * Having decided on that stuff, you also need to decide whether you will write to the output device/whatever</span></div>
<div class="line"><a id="l01226" name="l01226"></a><span class="lineno"> 1226</span><span class="comment"> * synchronously or asynchronously.  To wit, the thread safety discussion:</span></div>
<div class="line"><a id="l01227" name="l01227"></a><span class="lineno"> 1227</span><span class="comment"> *</span></div>
<div class="line"><a id="l01228" name="l01228"></a><span class="lineno"> 1228</span><span class="comment"> * ### Thread safety ###</span></div>
<div class="line"><a id="l01229" name="l01229"></a><span class="lineno"> 1229</span><span class="comment"> * The degree of thread safety for either of the 2 main operations is completely up to the subclass implementer.</span></div>
<div class="line"><a id="l01230" name="l01230"></a><span class="lineno"> 1230</span><span class="comment"> * Informally, we suggest here that you think about this topic carefully.  In particular, without locking,</span></div>
<div class="line"><a id="l01231" name="l01231"></a><span class="lineno"> 1231</span><span class="comment"> * do_log() may run concurrently with itself from multiple threads; depending on the medium to which</span></div>
<div class="line"><a id="l01232" name="l01232"></a><span class="lineno"> 1232</span><span class="comment"> * it is writing, this may result in corruption or ugly output or turn out fine, depending on how you define</span></div>
<div class="line"><a id="l01233" name="l01233"></a><span class="lineno"> 1233</span><span class="comment"> * &quot;fine.&quot;  Whether this is a concern or not is up to you.  Note, however, that in practice as of this writing</span></div>
<div class="line"><a id="l01234" name="l01234"></a><span class="lineno"> 1234</span><span class="comment"> * *at least* one Flow module (flow::net_flow) will definitely potentially execute should_log() and do_log()</span></div>
<div class="line"><a id="l01235" name="l01235"></a><span class="lineno"> 1235</span><span class="comment"> * concurrently with themselves from multiple threads on the same Logger.  In general that should be expected in all but</span></div>
<div class="line"><a id="l01236" name="l01236"></a><span class="lineno"> 1236</span><span class="comment"> * the simplest single-threaded apps.</span></div>
<div class="line"><a id="l01237" name="l01237"></a><span class="lineno"> 1237</span><span class="comment"> *</span></div>
<div class="line"><a id="l01238" name="l01238"></a><span class="lineno"> 1238</span><span class="comment"> * Implementation suggestions for Logger subclasses with respect to thread safety: There are 2 likeliest patterns one</span></div>
<div class="line"><a id="l01239" name="l01239"></a><span class="lineno"> 1239</span><span class="comment"> * can use.</span></div>
<div class="line"><a id="l01240" name="l01240"></a><span class="lineno"> 1240</span><span class="comment"> *   -# One can use a mutex lock around actual writing to the target device.  There&#39;s nothing inherently un-performant</span></div>
<div class="line"><a id="l01241" name="l01241"></a><span class="lineno"> 1241</span><span class="comment"> *      about this, in an of itself, and the implementation is incredibly simple.  For example see</span></div>
<div class="line"><a id="l01242" name="l01242"></a><span class="lineno"> 1242</span><span class="comment"> *      Simple_ostream_logger.  However, there *is* a significant performance danger if the device-writing itself can</span></div>
<div class="line"><a id="l01243" name="l01243"></a><span class="lineno"> 1243</span><span class="comment"> *      be both synchronous and slow.  In particular, a file write (when flushing any buffer such as the internal</span></div>
<div class="line"><a id="l01244" name="l01244"></a><span class="lineno"> 1244</span><span class="comment"> *      one in `FILE*` or `ofstream`), which is likely after each message, is usually synchronous and can be</span></div>
<div class="line"><a id="l01245" name="l01245"></a><span class="lineno"> 1245</span><span class="comment"> *      sporadically slow (consider having to spin up a sleeping hard drive for instance).  That would not only block</span></div>
<div class="line"><a id="l01246" name="l01246"></a><span class="lineno"> 1246</span><span class="comment"> *      the log-call-site thread but also any competing logging threads at that time.  That is probably fine in many</span></div>
<div class="line"><a id="l01247" name="l01247"></a><span class="lineno"> 1247</span><span class="comment"> *      non-production scenarios, but in a production heavy-duty server it&#39;s not OK.</span></div>
<div class="line"><a id="l01248" name="l01248"></a><span class="lineno"> 1248</span><span class="comment"> *      - An informal suggestion: It is fine for console output, probably (standard out, standard err).  Otherwise,</span></div>
<div class="line"><a id="l01249" name="l01249"></a><span class="lineno"> 1249</span><span class="comment"> *        particularly with files and synchronous networking, don&#39;t.  Use the following instead:</span></div>
<div class="line"><a id="l01250" name="l01250"></a><span class="lineno"> 1250</span><span class="comment"> *   -# One can avoid any such lock; instead the log-call-site thread can save the stuff to log (including the message</span></div>
<div class="line"><a id="l01251" name="l01251"></a><span class="lineno"> 1251</span><span class="comment"> *      and Msg_metadata passed to do_log()) and pass it to a dedicated thread (or pool thereof, etc.) in charge of</span></div>
<div class="line"><a id="l01252" name="l01252"></a><span class="lineno"> 1252</span><span class="comment"> *      asynchronously queueing up stuff to write to device and actually writing it in the order received at some</span></div>
<div class="line"><a id="l01253" name="l01253"></a><span class="lineno"> 1253</span><span class="comment"> *      later time (though typically fairly soon and definitely ASAP in most cases).  This is a bit more complex, but</span></div>
<div class="line"><a id="l01254" name="l01254"></a><span class="lineno"> 1254</span><span class="comment"> *      with flow::async it&#39;s really pretty easy still.  See the heavy-duty Async_file_logger for example.</span></div>
<div class="line"><a id="l01255" name="l01255"></a><span class="lineno"> 1255</span><span class="comment"> *</span></div>
<div class="line"><a id="l01256" name="l01256"></a><span class="lineno"> 1256</span><span class="comment"> * Both general patterns are formally supported.  To use pattern 1, have your Logger implementation&#39;s</span></div>
<div class="line"><a id="l01257" name="l01257"></a><span class="lineno"> 1257</span><span class="comment"> * logs_asynchronously() return `false`.  To use pattern 2, have it use `true`.  The precise implications are</span></div>
<div class="line"><a id="l01258" name="l01258"></a><span class="lineno"> 1258</span><span class="comment"> * documented in doc header of do_log().</span></div>
<div class="line"><a id="l01259" name="l01259"></a><span class="lineno"> 1259</span><span class="comment"> *</span></div>
<div class="line"><a id="l01260" name="l01260"></a><span class="lineno"> 1260</span><span class="comment"> * ### Order of output requirements ###</span></div>
<div class="line"><a id="l01261" name="l01261"></a><span class="lineno"> 1261</span><span class="comment"> * We assume for this discussion that the notion of order of final output (to device/file/network/whatever) exists,</span></div>
<div class="line"><a id="l01262" name="l01262"></a><span class="lineno"> 1262</span><span class="comment"> * and that the Logger implementation indeed safely outputs message M1 entirely before M2, or vice versa, for every</span></div>
<div class="line"><a id="l01263" name="l01263"></a><span class="lineno"> 1263</span><span class="comment"> * pair of messages (in this context by message we mean message+metadata pair) ever passed to do_log().  With that</span></div>
<div class="line"><a id="l01264" name="l01264"></a><span class="lineno"> 1264</span><span class="comment"> * assumption in effect (IF indeed it is), the present text *requires* that the following is guaranteed:</span></div>
<div class="line"><a id="l01265" name="l01265"></a><span class="lineno"> 1265</span><span class="comment"> *   - In a given thread T, for a given Logger L, if `L.do_log(M1);` is called before `L.do_log(M2)`, and both</span></div>
<div class="line"><a id="l01266" name="l01266"></a><span class="lineno"> 1266</span><span class="comment"> *     are successfully output by L, then the final output order must have M1 precede M2, not vice versa.</span></div>
<div class="line"><a id="l01267" name="l01267"></a><span class="lineno"> 1267</span><span class="comment"> *   - If, instead, M1 is logged in thread T1, while M2 is logged in thread T2:</span></div>
<div class="line"><a id="l01268" name="l01268"></a><span class="lineno"> 1268</span><span class="comment"> *     - If the 2 do_log() calls are chronologically disjoint, then again the final output must also have</span></div>
<div class="line"><a id="l01269" name="l01269"></a><span class="lineno"> 1269</span><span class="comment"> *       M1 precede M2 if M1 went first; and vice versa.</span></div>
<div class="line"><a id="l01270" name="l01270"></a><span class="lineno"> 1270</span><span class="comment"> *     - If the 2 do_log() calls chronologically overlap, then either final output order is acceptable.</span></div>
<div class="line"><a id="l01271" name="l01271"></a><span class="lineno"> 1271</span><span class="comment"> *       (Ideally, it *should* reflect the order of entry to do_log() in the 2 threads, but it&#39;s formally optional.</span></div>
<div class="line"><a id="l01272" name="l01272"></a><span class="lineno"> 1272</span><span class="comment"> *       Informally this typically will happen anyway under most basic algorithms imaginable.)</span></div>
<div class="line"><a id="l01273" name="l01273"></a><span class="lineno"> 1273</span><span class="comment"> *</span></div>
<div class="line"><a id="l01274" name="l01274"></a><span class="lineno"> 1274</span><span class="comment"> * Note that this is only tangentially related to any time stamps one might see in the final output.</span></div>
<div class="line"><a id="l01275" name="l01275"></a><span class="lineno"> 1275</span><span class="comment"> *</span></div>
<div class="line"><a id="l01276" name="l01276"></a><span class="lineno"> 1276</span><span class="comment"> * See also notes on log output order in FLOW_LOG_WARNING() doc header (which applies to all log call sites).</span></div>
<div class="line"><a id="l01277" name="l01277"></a><span class="lineno"> 1277</span><span class="comment"> * The behavior described there is a function of the underlying Logger following the above formal requirements for</span></div>
<div class="line"><a id="l01278" name="l01278"></a><span class="lineno"> 1278</span><span class="comment"> * thread-safe Logger implementations.</span></div>
<div class="line"><a id="l01279" name="l01279"></a><span class="lineno"> 1279</span><span class="comment"> */</span></div>
<div class="line"><a id="l01280" name="l01280"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Logger.html"> 1280</a></span><span class="keyword">class </span><a class="code hl_class" href="classflow_1_1log_1_1Logger.html">Logger</a> :</div>
<div class="line"><a id="l01281" name="l01281"></a><span class="lineno"> 1281</span>  <span class="keyword">public</span> <a class="code hl_class" href="classflow_1_1util_1_1Null__interface.html">util::Null_interface</a>,</div>
<div class="line"><a id="l01282" name="l01282"></a><span class="lineno"> 1282</span>  <span class="keyword">public</span> <a class="code hl_class" href="classflow_1_1util_1_1Unique__id__holder.html">util::Unique_id_holder</a>,</div>
<div class="line"><a id="l01283" name="l01283"></a><span class="lineno"> 1283</span>  <span class="keyword">private</span> boost::noncopyable <span class="comment">// Though it&#39;s an interface, this just seems like a prudent rule.  @todo Reconsider?</span></div>
<div class="line"><a id="l01284" name="l01284"></a><span class="lineno"> 1284</span>{</div>
<div class="line"><a id="l01285" name="l01285"></a><span class="lineno"> 1285</span><span class="keyword">public</span>:</div>
<div class="line"><a id="l01286" name="l01286"></a><span class="lineno"> 1286</span>  <span class="comment">// Methods.</span></div>
<div class="line"><a id="l01287" name="l01287"></a><span class="lineno"> 1287</span><span class="comment"></span> </div>
<div class="line"><a id="l01288" name="l01288"></a><span class="lineno"> 1288</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01289" name="l01289"></a><span class="lineno"> 1289</span><span class="comment">   * Given attributes of a hypothetical message that would be logged, return `true` if that message</span></div>
<div class="line"><a id="l01290" name="l01290"></a><span class="lineno"> 1290</span><span class="comment">   * should be logged and `false` otherwise (e.g., if the verbosity of the message is above the</span></div>
<div class="line"><a id="l01291" name="l01291"></a><span class="lineno"> 1291</span><span class="comment">   * current configured verbosity threshold for the Component specified).</span></div>
<div class="line"><a id="l01292" name="l01292"></a><span class="lineno"> 1292</span><span class="comment">   *</span></div>
<div class="line"><a id="l01293" name="l01293"></a><span class="lineno"> 1293</span><span class="comment">   * The convenience macros `FLOW_LOG_...()` combine this with do_log() to make it so that</span></div>
<div class="line"><a id="l01294" name="l01294"></a><span class="lineno"> 1294</span><span class="comment">   * a message is only built if `should_log() == true`, and (if so) builds and logs it; otherwise</span></div>
<div class="line"><a id="l01295" name="l01295"></a><span class="lineno"> 1295</span><span class="comment">   * almost no computing or storage resources are spent, and the message is neither built nor logged logged.</span></div>
<div class="line"><a id="l01296" name="l01296"></a><span class="lineno"> 1296</span><span class="comment">   * The verb &quot;to build message&quot; here more formally means &quot;to execute the `ostream&lt;&lt;` fragment passed to macro by</span></div>
<div class="line"><a id="l01297" name="l01297"></a><span class="lineno"> 1297</span><span class="comment">   * writing characters to some internally maintained `ostream` accordingly.&quot;</span></div>
<div class="line"><a id="l01298" name="l01298"></a><span class="lineno"> 1298</span><span class="comment">   *</span></div>
<div class="line"><a id="l01299" name="l01299"></a><span class="lineno"> 1299</span><span class="comment">   * @param sev</span></div>
<div class="line"><a id="l01300" name="l01300"></a><span class="lineno"> 1300</span><span class="comment">   *        Severity of the message.</span></div>
<div class="line"><a id="l01301" name="l01301"></a><span class="lineno"> 1301</span><span class="comment">   * @param component</span></div>
<div class="line"><a id="l01302" name="l01302"></a><span class="lineno"> 1302</span><span class="comment">   *        Component of the message.  Reminder: `component.empty() == true` is allowed; which isn&#39;t to say it will</span></div>
<div class="line"><a id="l01303" name="l01303"></a><span class="lineno"> 1303</span><span class="comment">   *        or won&#39;t result in this method returning `true`, but that it will return and not act in undefined fashion.</span></div>
<div class="line"><a id="l01304" name="l01304"></a><span class="lineno"> 1304</span><span class="comment">   * @return `true` if it should be logged; `false` if it should not.</span></div>
<div class="line"><a id="l01305" name="l01305"></a><span class="lineno"> 1305</span><span class="comment">   */</span></div>
<div class="line"><a id="l01306" name="l01306"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Logger.html#ac8a2e7a33fe3fbc0c29ead62ed98c022"> 1306</a></span>  <span class="keyword">virtual</span> <span class="keywordtype">bool</span> <a class="code hl_function" href="classflow_1_1log_1_1Logger.html#ac8a2e7a33fe3fbc0c29ead62ed98c022">should_log</a>(<a class="code hl_enumeration" href="namespaceflow_1_1log.html#a5c602384e6fe9d7642740ac2fae4ad04">Sev</a> sev, <span class="keyword">const</span> <a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a>&amp; component) <span class="keyword">const</span> = 0;</div>
<div class="line"><a id="l01307" name="l01307"></a><span class="lineno"> 1307</span><span class="comment"></span> </div>
<div class="line"><a id="l01308" name="l01308"></a><span class="lineno"> 1308</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01309" name="l01309"></a><span class="lineno"> 1309</span><span class="comment">   * Must return `true` if do_log() at least sometimes logs the given message and metadata (e.g., time stamp) after</span></div>
<div class="line"><a id="l01310" name="l01310"></a><span class="lineno"> 1310</span><span class="comment">   * do_log() returns; `false` if this never occurs (i.e., it logs synchronously, always).  do_log() doc header</span></div>
<div class="line"><a id="l01311" name="l01311"></a><span class="lineno"> 1311</span><span class="comment">   * formally describes the implications of this.</span></div>
<div class="line"><a id="l01312" name="l01312"></a><span class="lineno"> 1312</span><span class="comment">   *</span></div>
<div class="line"><a id="l01313" name="l01313"></a><span class="lineno"> 1313</span><span class="comment">   * This must always return the same value, for a given `*this`.</span></div>
<div class="line"><a id="l01314" name="l01314"></a><span class="lineno"> 1314</span><span class="comment">   *</span></div>
<div class="line"><a id="l01315" name="l01315"></a><span class="lineno"> 1315</span><span class="comment">   * This method is intended for internal use by the flow::log system; informally it is not expected the user</span></div>
<div class="line"><a id="l01316" name="l01316"></a><span class="lineno"> 1316</span><span class="comment">   * will call it.  Technically there is no harm in doing so.  (It would have been `private` but cannot due to certain</span></div>
<div class="line"><a id="l01317" name="l01317"></a><span class="lineno"> 1317</span><span class="comment">   * C++ limitations, and certain contrived ways to do it are just not worth the trouble.)</span></div>
<div class="line"><a id="l01318" name="l01318"></a><span class="lineno"> 1318</span><span class="comment">   *</span></div>
<div class="line"><a id="l01319" name="l01319"></a><span class="lineno"> 1319</span><span class="comment">   * @internal</span></div>
<div class="line"><a id="l01320" name="l01320"></a><span class="lineno"> 1320</span><span class="comment">   * The &quot;certain C++ limitations&quot; are that FLOW_LOG_WITHOUT_CHECKING() must access it, but it is a macro and cannot</span></div>
<div class="line"><a id="l01321" name="l01321"></a><span class="lineno"> 1321</span><span class="comment">   * be involved in `friend`ship.  A contrived way to resolve it would be to make some `detail/` helper free function</span></div>
<div class="line"><a id="l01322" name="l01322"></a><span class="lineno"> 1322</span><span class="comment">   * the `friend`, which would call this method, and invoke that free function from the macro.  All that just to move a</span></div>
<div class="line"><a id="l01323" name="l01323"></a><span class="lineno"> 1323</span><span class="comment">   * harmless thing into `private` -- I think not worth it, but an argument could be made.</span></div>
<div class="line"><a id="l01324" name="l01324"></a><span class="lineno"> 1324</span><span class="comment">   * @endinternal</span></div>
<div class="line"><a id="l01325" name="l01325"></a><span class="lineno"> 1325</span><span class="comment">   *</span></div>
<div class="line"><a id="l01326" name="l01326"></a><span class="lineno"> 1326</span><span class="comment">   * @see do_log().</span></div>
<div class="line"><a id="l01327" name="l01327"></a><span class="lineno"> 1327</span><span class="comment">   * @return See above.</span></div>
<div class="line"><a id="l01328" name="l01328"></a><span class="lineno"> 1328</span><span class="comment">   */</span></div>
<div class="line"><a id="l01329" name="l01329"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Logger.html#ae04868e2a384e60a349ecba8340cd731"> 1329</a></span>  <span class="keyword">virtual</span> <span class="keywordtype">bool</span> <a class="code hl_function" href="classflow_1_1log_1_1Logger.html#ae04868e2a384e60a349ecba8340cd731">logs_asynchronously</a>() <span class="keyword">const</span> = 0;</div>
<div class="line"><a id="l01330" name="l01330"></a><span class="lineno"> 1330</span><span class="comment"></span> </div>
<div class="line"><a id="l01331" name="l01331"></a><span class="lineno"> 1331</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01332" name="l01332"></a><span class="lineno"> 1332</span><span class="comment">   * Given a message and its severity, logs that message and possibly severity WITHOUT checking whether it should be</span></div>
<div class="line"><a id="l01333" name="l01333"></a><span class="lineno"> 1333</span><span class="comment">   * logged (i.e., without performing logic that should_log() performs).  The logging is guaranteed to be synchronous</span></div>
<div class="line"><a id="l01334" name="l01334"></a><span class="lineno"> 1334</span><span class="comment">   * if `!logs_asynchronously()`; but may be asynchronous otherwise (more on this below).</span></div>
<div class="line"><a id="l01335" name="l01335"></a><span class="lineno"> 1335</span><span class="comment">   *</span></div>
<div class="line"><a id="l01336" name="l01336"></a><span class="lineno"> 1336</span><span class="comment">   * The convenience macros `FLOW_LOG_...()` combine this with should_log() to make it so that a</span></div>
<div class="line"><a id="l01337" name="l01337"></a><span class="lineno"> 1337</span><span class="comment">   * message is only constructed if `should_log() == true`, and if so, constructs and logs it; otherwise</span></div>
<div class="line"><a id="l01338" name="l01338"></a><span class="lineno"> 1338</span><span class="comment">   * almost no computing or storage resources are spent, and the message is not logged.</span></div>
<div class="line"><a id="l01339" name="l01339"></a><span class="lineno"> 1339</span><span class="comment">   *</span></div>
<div class="line"><a id="l01340" name="l01340"></a><span class="lineno"> 1340</span><span class="comment">   * Expectations of what should or should not be included in `msg` are of some importance.</span></div>
<div class="line"><a id="l01341" name="l01341"></a><span class="lineno"> 1341</span><span class="comment">   * They are as follows.  To summarize, `msg` should include the message (as specified typically as the</span></div>
<div class="line"><a id="l01342" name="l01342"></a><span class="lineno"> 1342</span><span class="comment">   * `ARG_stream_fragment` arg to FLOW_LOG_WARNING() and buddies); and `*msg_metadata` should include everything</span></div>
<div class="line"><a id="l01343" name="l01343"></a><span class="lineno"> 1343</span><span class="comment">   * else.  This design provides maximum flexibility to the Logger::do_log() implementation to structure the final</span></div>
<div class="line"><a id="l01344" name="l01344"></a><span class="lineno"> 1344</span><span class="comment">   * output&#39;s contents (in the log file, or console, or wherever) as it sees fit, cosmetically and size-wise.</span></div>
<div class="line"><a id="l01345" name="l01345"></a><span class="lineno"> 1345</span><span class="comment">   *</span></div>
<div class="line"><a id="l01346" name="l01346"></a><span class="lineno"> 1346</span><span class="comment">   * Note on trailing newline(s): `msg` must include any trailing newline(s) that are *required* to be output.</span></div>
<div class="line"><a id="l01347" name="l01347"></a><span class="lineno"> 1347</span><span class="comment">   * By convention, do_log() itself will print a message terminator (often in fact a newline) after each message, if</span></div>
<div class="line"><a id="l01348" name="l01348"></a><span class="lineno"> 1348</span><span class="comment">   * applicable.  Hence typically there is no trailing newline at the end of most `msg`s, and one would include N of</span></div>
<div class="line"><a id="l01349" name="l01349"></a><span class="lineno"> 1349</span><span class="comment">   * them if and only if one intentionally desires N trailing blank lines (possible but atypical).</span></div>
<div class="line"><a id="l01350" name="l01350"></a><span class="lineno"> 1350</span><span class="comment">   *</span></div>
<div class="line"><a id="l01351" name="l01351"></a><span class="lineno"> 1351</span><span class="comment">   * ### Precise meaning of logs_asynchronously() ###</span></div>
<div class="line"><a id="l01352" name="l01352"></a><span class="lineno"> 1352</span><span class="comment">   * Let ASYNC = the value logs_asynchronously() returns (note for a given `*this` it must always be the same value by</span></div>
<div class="line"><a id="l01353" name="l01353"></a><span class="lineno"> 1353</span><span class="comment">   * that API&#39;s contract).  Then do_log() must act as follows:</span></div>
<div class="line"><a id="l01354" name="l01354"></a><span class="lineno"> 1354</span><span class="comment">   *   - If ASYNC is `false`: Do not make a copy of `msg`; output it synchronously.  Do not make a copy of `*metadata`.</span></div>
<div class="line"><a id="l01355" name="l01355"></a><span class="lineno"> 1355</span><span class="comment">   *     Do not `delete metadata`.  Output any of its contents synchronously.</span></div>
<div class="line"><a id="l01356" name="l01356"></a><span class="lineno"> 1356</span><span class="comment">   *   - If ASYNC is `true`: Optionally make a copy of `msg`, unless you are able to output it synchronously, in which</span></div>
<div class="line"><a id="l01357" name="l01357"></a><span class="lineno"> 1357</span><span class="comment">   *     case there is no need.  Do not make a copy of `*metadata`.  You *must* `delete metadata` at some point;</span></div>
<div class="line"><a id="l01358" name="l01358"></a><span class="lineno"> 1358</span><span class="comment">   *     failing to do so *will* leak it.  (Note: We are intentionally avoiding using `shared_ptr` or even `unique_ptr`,</span></div>
<div class="line"><a id="l01359" name="l01359"></a><span class="lineno"> 1359</span><span class="comment">   *     for the perf savings, since logging is ubiquitous.)  Output `*metadata` contents either synchronously or</span></div>
<div class="line"><a id="l01360" name="l01360"></a><span class="lineno"> 1360</span><span class="comment">   *     asynchronously.</span></div>
<div class="line"><a id="l01361" name="l01361"></a><span class="lineno"> 1361</span><span class="comment">   *</span></div>
<div class="line"><a id="l01362" name="l01362"></a><span class="lineno"> 1362</span><span class="comment">   * The only formal requirement, however, is simply: You must `delete metadata;` at some future point &lt;=iff=&gt;</span></div>
<div class="line"><a id="l01363" name="l01363"></a><span class="lineno"> 1363</span><span class="comment">   * ASYNC is `true`.  The other requirements just above are informal but of no less import.</span></div>
<div class="line"><a id="l01364" name="l01364"></a><span class="lineno"> 1364</span><span class="comment">   *</span></div>
<div class="line"><a id="l01365" name="l01365"></a><span class="lineno"> 1365</span><span class="comment">   * @see Msg_metadata which includes stuff not to include in `msg`.</span></div>
<div class="line"><a id="l01366" name="l01366"></a><span class="lineno"> 1366</span><span class="comment">   *</span></div>
<div class="line"><a id="l01367" name="l01367"></a><span class="lineno"> 1367</span><span class="comment">   * @param metadata</span></div>
<div class="line"><a id="l01368" name="l01368"></a><span class="lineno"> 1368</span><span class="comment">   *        All information to potentially log in addition to `msg`.</span></div>
<div class="line"><a id="l01369" name="l01369"></a><span class="lineno"> 1369</span><span class="comment">   * @param msg</span></div>
<div class="line"><a id="l01370" name="l01370"></a><span class="lineno"> 1370</span><span class="comment">   *        The message.  See details above.  Short version: exclude anything from `metadata`; exclude any ever-present</span></div>
<div class="line"><a id="l01371" name="l01371"></a><span class="lineno"> 1371</span><span class="comment">   *        terminating newline.</span></div>
<div class="line"><a id="l01372" name="l01372"></a><span class="lineno"> 1372</span><span class="comment">   */</span></div>
<div class="line"><a id="l01373" name="l01373"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Logger.html#a934667f16dd6ca0841e521296ab3a6e2"> 1373</a></span>  <span class="keyword">virtual</span> <span class="keywordtype">void</span> <a class="code hl_function" href="classflow_1_1log_1_1Logger.html#a934667f16dd6ca0841e521296ab3a6e2">do_log</a>(<a class="code hl_struct" href="structflow_1_1log_1_1Msg__metadata.html">Msg_metadata</a>* metadata, <a class="code hl_typedef" href="namespaceflow_1_1util.html#ae4dc52186797094b3040379ff19124c9">util::String_view</a> msg) = 0;</div>
<div class="line"><a id="l01374" name="l01374"></a><span class="lineno"> 1374</span><span class="comment"></span> </div>
<div class="line"><a id="l01375" name="l01375"></a><span class="lineno"> 1375</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01376" name="l01376"></a><span class="lineno"> 1376</span><span class="comment">   * Sets or unsets the current thread&#39;s logging-worthy string name; optionally sets the OS thread name (such as</span></div>
<div class="line"><a id="l01377" name="l01377"></a><span class="lineno"> 1377</span><span class="comment">   * visible in `top` output).  The logging-worthy name is always set or unset; the OS name is modified only if</span></div>
<div class="line"><a id="l01378" name="l01378"></a><span class="lineno"> 1378</span><span class="comment">   * `also_set_os_name == true` arg is set.  `thread_nickname` can thus be set to something more descriptive than</span></div>
<div class="line"><a id="l01379" name="l01379"></a><span class="lineno"> 1379</span><span class="comment">   * any default, such as: &quot;native_main&quot; or &quot;worker_port_2231.&quot;</span></div>
<div class="line"><a id="l01380" name="l01380"></a><span class="lineno"> 1380</span><span class="comment">   *</span></div>
<div class="line"><a id="l01381" name="l01381"></a><span class="lineno"> 1381</span><span class="comment">   *   - The logging-worthy thread string name is accessed as follows:</span></div>
<div class="line"><a id="l01382" name="l01382"></a><span class="lineno"> 1382</span><span class="comment">   *     - `FLOW_LOG_*()` macros pass it automatically to the appropriate log::Logger.  All out-of-the-box `Logger`s</span></div>
<div class="line"><a id="l01383" name="l01383"></a><span class="lineno"> 1383</span><span class="comment">   *       will then log either the name set here (if not blank) or the thread ID (if blank).  (Custom `Logger`s</span></div>
<div class="line"><a id="l01384" name="l01384"></a><span class="lineno"> 1384</span><span class="comment">   *       can ignore these data and not log them; but presumably most will at least optionally log them.)</span></div>
<div class="line"><a id="l01385" name="l01385"></a><span class="lineno"> 1385</span><span class="comment">   *     - It can also be obtained directly via this_thread_logged_name_os_manip(), set_thread_info(), or</span></div>
<div class="line"><a id="l01386" name="l01386"></a><span class="lineno"> 1386</span><span class="comment">   *       set_thread_info_in_msg_metadata().</span></div>
<div class="line"><a id="l01387" name="l01387"></a><span class="lineno"> 1387</span><span class="comment">   *   - The OS thread name can be accessed in various ways; including in Linux:</span></div>
<div class="line"><a id="l01388" name="l01388"></a><span class="lineno"> 1388</span><span class="comment">   *     - `ps H -C $cmd -o pid\ tid\ cmd\ comm  # The comm column will be the thread name; set $proc = process name.`</span></div>
<div class="line"><a id="l01389" name="l01389"></a><span class="lineno"> 1389</span><span class="comment">   *     - `top -H` (thread mode -- or just `top` and press H key for the same effect).</span></div>
<div class="line"><a id="l01390" name="l01390"></a><span class="lineno"> 1390</span><span class="comment">   *</span></div>
<div class="line"><a id="l01391" name="l01391"></a><span class="lineno"> 1391</span><span class="comment">   * More precisely, there are 3 states for each thread: before this_thread_set_logged_nickname() is called;</span></div>
<div class="line"><a id="l01392" name="l01392"></a><span class="lineno"> 1392</span><span class="comment">   * after it is called with blank name; and after it&#39;s called non-blank name.  The semantics are as follows:</span></div>
<div class="line"><a id="l01393" name="l01393"></a><span class="lineno"> 1393</span><span class="comment">   *   - Logging-worthy thread string name:</span></div>
<div class="line"><a id="l01394" name="l01394"></a><span class="lineno"> 1394</span><span class="comment">   *     - Initial: As-if this_thread_set_logged_nickname() was already called with blank name (next bullet).</span></div>
<div class="line"><a id="l01395" name="l01395"></a><span class="lineno"> 1395</span><span class="comment">   *     - Blank: The thread string name becomes conceptually null; and the thread ID shall be used instead.</span></div>
<div class="line"><a id="l01396" name="l01396"></a><span class="lineno"> 1396</span><span class="comment">   *     - Non-blank: The thread string name becomes equal to `thread_nickname`.</span></div>
<div class="line"><a id="l01397" name="l01397"></a><span class="lineno"> 1397</span><span class="comment">   *   - OS thread name:</span></div>
<div class="line"><a id="l01398" name="l01398"></a><span class="lineno"> 1398</span><span class="comment">   *     - Initial: `ps`, `top`, etc. will show the thread name as equal to the process name.</span></div>
<div class="line"><a id="l01399" name="l01399"></a><span class="lineno"> 1399</span><span class="comment">   *     - Blank: `ps`, `top`, etc. will show the thread name as the thread ID (truncated to N characters, though</span></div>
<div class="line"><a id="l01400" name="l01400"></a><span class="lineno"> 1400</span><span class="comment">   *       this is unlikely to be exceeded by real thread IDs).</span></div>
<div class="line"><a id="l01401" name="l01401"></a><span class="lineno"> 1401</span><span class="comment">   *     - Non-blank: `ps`, `top`, etc. will show the thread name as equal to `thread_nickname` (truncated to N</span></div>
<div class="line"><a id="l01402" name="l01402"></a><span class="lineno"> 1402</span><span class="comment">   *       characters).</span></div>
<div class="line"><a id="l01403" name="l01403"></a><span class="lineno"> 1403</span><span class="comment">   *     - Note: Because &quot;Initial&quot; and &quot;Blank&quot; are necessarily not the same, it is recommended to call</span></div>
<div class="line"><a id="l01404" name="l01404"></a><span class="lineno"> 1404</span><span class="comment">   *       this_thread_set_logged_nickname() around thread creation time even if `thread_nickname` is blank.</span></div>
<div class="line"><a id="l01405" name="l01405"></a><span class="lineno"> 1405</span><span class="comment">   *       Then `ps`, `top`, etc. output will still be useful and possible to cross-reference with log output, say.</span></div>
<div class="line"><a id="l01406" name="l01406"></a><span class="lineno"> 1406</span><span class="comment">   *     - Note: N is documented in `man pthread_setname_np` as 15 not counting the NUL terminator.</span></div>
<div class="line"><a id="l01407" name="l01407"></a><span class="lineno"> 1407</span><span class="comment">   *       Therefore ideally keep the `thread_nickname.size()` to at most N.</span></div>
<div class="line"><a id="l01408" name="l01408"></a><span class="lineno"> 1408</span><span class="comment">   *</span></div>
<div class="line"><a id="l01409" name="l01409"></a><span class="lineno"> 1409</span><span class="comment">   * ### Performance ###</span></div>
<div class="line"><a id="l01410" name="l01410"></a><span class="lineno"> 1410</span><span class="comment">   * Subsequently obtaining the nickname involves a linear string copy;</span></div>
<div class="line"><a id="l01411" name="l01411"></a><span class="lineno"> 1411</span><span class="comment">   * the cost of this is worth considering given that this is potentially</span></div>
<div class="line"><a id="l01412" name="l01412"></a><span class="lineno"> 1412</span><span class="comment">   * done for every single log call site, if the nickname is indeed set.  However, most `string` implementations</span></div>
<div class="line"><a id="l01413" name="l01413"></a><span class="lineno"> 1413</span><span class="comment">   * provide an optimization that uses a `union` (or equivalent) technique to store short strings in the same place</span></div>
<div class="line"><a id="l01414" name="l01414"></a><span class="lineno"> 1414</span><span class="comment">   * as the data members (pointer, size, capacity) required for long strings; meaning such short `string`s cost no</span></div>
<div class="line"><a id="l01415" name="l01415"></a><span class="lineno"> 1415</span><span class="comment">   * more to copy than an *empty* one does.  In gcc 5, this is 15 bytes or `char`s, but implementations vary.</span></div>
<div class="line"><a id="l01416" name="l01416"></a><span class="lineno"> 1416</span><span class="comment">   *</span></div>
<div class="line"><a id="l01417" name="l01417"></a><span class="lineno"> 1417</span><span class="comment">   * Therefore, it is *actively encouraged* that you keep the length of `thread_nickname` low.  &quot;Low&quot; depends on the</span></div>
<div class="line"><a id="l01418" name="l01418"></a><span class="lineno"> 1418</span><span class="comment">   * compiler, but keeping it somewhere at or under 15 characters is likely good.  If you do so, the effective cost</span></div>
<div class="line"><a id="l01419" name="l01419"></a><span class="lineno"> 1419</span><span class="comment">   * (at a log call site) will be the same as if `thread_nickname.empty()`, so one could not do better.</span></div>
<div class="line"><a id="l01420" name="l01420"></a><span class="lineno"> 1420</span><span class="comment">   * Note, also, that the OS-name (in Linux) max length happens to also be 15 (see N discussion above), so there is</span></div>
<div class="line"><a id="l01421" name="l01421"></a><span class="lineno"> 1421</span><span class="comment">   * convenient synergy there.</span></div>
<div class="line"><a id="l01422" name="l01422"></a><span class="lineno"> 1422</span><span class="comment">   *</span></div>
<div class="line"><a id="l01423" name="l01423"></a><span class="lineno"> 1423</span><span class="comment">   * ### Thready safety ###</span></div>
<div class="line"><a id="l01424" name="l01424"></a><span class="lineno"> 1424</span><span class="comment">   * This call is safe w/r/t concurrent execution with itself and this_thread_logged_name_os_manip() in other</span></div>
<div class="line"><a id="l01425" name="l01425"></a><span class="lineno"> 1425</span><span class="comment">   * thread(s) for a given `*this`.  It is thread-local in nature.</span></div>
<div class="line"><a id="l01426" name="l01426"></a><span class="lineno"> 1426</span><span class="comment">   *</span></div>
<div class="line"><a id="l01427" name="l01427"></a><span class="lineno"> 1427</span><span class="comment">   * ### Naming rationale ###</span></div>
<div class="line"><a id="l01428" name="l01428"></a><span class="lineno"> 1428</span><span class="comment">   * this_thread_set_logged_nickname() is an incomplete name, in that it (optionally) also affects the OS thread name.</span></div>
<div class="line"><a id="l01429" name="l01429"></a><span class="lineno"> 1429</span><span class="comment">   * The function was not renamed for compatibility reasons, as the technically incomplete name is in my (ygoldfel)</span></div>
<div class="line"><a id="l01430" name="l01430"></a><span class="lineno"> 1430</span><span class="comment">   * opinion still acceptably descriptive.</span></div>
<div class="line"><a id="l01431" name="l01431"></a><span class="lineno"> 1431</span><span class="comment">   *</span></div>
<div class="line"><a id="l01432" name="l01432"></a><span class="lineno"> 1432</span><span class="comment">   * @param thread_nickname</span></div>
<div class="line"><a id="l01433" name="l01433"></a><span class="lineno"> 1433</span><span class="comment">   *        New nickname of thread; or &quot;&quot; to request the thread to not be nicknamed (thread ID will be used).</span></div>
<div class="line"><a id="l01434" name="l01434"></a><span class="lineno"> 1434</span><span class="comment">   *        In the &quot;&quot; case, no particular thread ID format should ever be assumed; it may be OS-dependent;</span></div>
<div class="line"><a id="l01435" name="l01435"></a><span class="lineno"> 1435</span><span class="comment">   *        but it can be informally assumed to be useful for thread identification purposes (probably unique per thread</span></div>
<div class="line"><a id="l01436" name="l01436"></a><span class="lineno"> 1436</span><span class="comment">   *        and somewhat readable, etc.).  The non-blank value is copied and saved.</span></div>
<div class="line"><a id="l01437" name="l01437"></a><span class="lineno"> 1437</span><span class="comment">   * @param logger_ptr</span></div>
<div class="line"><a id="l01438" name="l01438"></a><span class="lineno"> 1438</span><span class="comment">   *        If non-null, this `Logger` will be used to log an INFO-severity message indicating the</span></div>
<div class="line"><a id="l01439" name="l01439"></a><span class="lineno"> 1439</span><span class="comment">   *        thread ID and new nickname (conceptually: [INFO] T...nickname...: Thread ...ID... has new nickname.).</span></div>
<div class="line"><a id="l01440" name="l01440"></a><span class="lineno"> 1440</span><span class="comment">   *        If null, nothing is logged.</span></div>
<div class="line"><a id="l01441" name="l01441"></a><span class="lineno"> 1441</span><span class="comment">   * @param also_set_os_name</span></div>
<div class="line"><a id="l01442" name="l01442"></a><span class="lineno"> 1442</span><span class="comment">   *        If and only `true`, `thread_nickname` (whether blank or not) also affects the current OS thread name.</span></div>
<div class="line"><a id="l01443" name="l01443"></a><span class="lineno"> 1443</span><span class="comment">   *        Otherwise it is not affected.</span></div>
<div class="line"><a id="l01444" name="l01444"></a><span class="lineno"> 1444</span><span class="comment">   *</span></div>
<div class="line"><a id="l01445" name="l01445"></a><span class="lineno"> 1445</span><span class="comment">   * @todo this_thread_set_logged_nickname() could take multiple `Logger`s, since it is an app-wide function</span></div>
<div class="line"><a id="l01446" name="l01446"></a><span class="lineno"> 1446</span><span class="comment">   * and potentially would want to be reflected in multiple loggers.  It could take a pair of iterators</span></div>
<div class="line"><a id="l01447" name="l01447"></a><span class="lineno"> 1447</span><span class="comment">   * or a container (in both cases, of template argument type).  Arguably, though, this is overkill; as (1) most code</span></div>
<div class="line"><a id="l01448" name="l01448"></a><span class="lineno"> 1448</span><span class="comment">   * paths deal with only one `get_logger()`-owning object each; (2) naming of a thread is obvious enough in subsequent</span></div>
<div class="line"><a id="l01449" name="l01449"></a><span class="lineno"> 1449</span><span class="comment">   * logs (hence this message only calls attention to that operation plus notes the thread ID before the nickname</span></div>
<div class="line"><a id="l01450" name="l01450"></a><span class="lineno"> 1450</span><span class="comment">   * assignment, not necessarily the most critical of information).  Certainly this zero-to-one-`Logger` version must</span></div>
<div class="line"><a id="l01451" name="l01451"></a><span class="lineno"> 1451</span><span class="comment">   * continue to be available for syntactic-sugary convenience, even if the to-do is performed.</span></div>
<div class="line"><a id="l01452" name="l01452"></a><span class="lineno"> 1452</span><span class="comment">   */</span></div>
<div class="line"><a id="l01453" name="l01453"></a><span class="lineno"> 1453</span>  <span class="keyword">static</span> <span class="keywordtype">void</span> <a class="code hl_function" href="classflow_1_1log_1_1Logger.html#a5600c71ccaa294650c7d34b596d90bf5">this_thread_set_logged_nickname</a>(<a class="code hl_typedef" href="namespaceflow_1_1util.html#ae4dc52186797094b3040379ff19124c9">util::String_view</a> thread_nickname = <a class="code hl_typedef" href="namespaceflow_1_1util.html#ae4dc52186797094b3040379ff19124c9">util::String_view</a>(),</div>
<div class="line"><a id="l01454" name="l01454"></a><span class="lineno"> 1454</span>                                              <a class="code hl_class" href="classflow_1_1log_1_1Logger.html">Logger</a>* logger_ptr = 0,</div>
<div class="line"><a id="l01455" name="l01455"></a><span class="lineno"> 1455</span>                                              <span class="keywordtype">bool</span> also_set_os_name = <span class="keyword">true</span>);</div>
<div class="line"><a id="l01456" name="l01456"></a><span class="lineno"> 1456</span><span class="comment"></span> </div>
<div class="line"><a id="l01457" name="l01457"></a><span class="lineno"> 1457</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01458" name="l01458"></a><span class="lineno"> 1458</span><span class="comment">   * `ostream` manipulator function that, if output via `operator&lt;&lt;` to an `ostream`, will cause the current</span></div>
<div class="line"><a id="l01459" name="l01459"></a><span class="lineno"> 1459</span><span class="comment">   * thread&#39;s logging-worthy string name to be output to that stream.  See this_thread_set_logged_nickname()</span></div>
<div class="line"><a id="l01460" name="l01460"></a><span class="lineno"> 1460</span><span class="comment">   * for details of what this string will actually be.</span></div>
<div class="line"><a id="l01461" name="l01461"></a><span class="lineno"> 1461</span><span class="comment">   *</span></div>
<div class="line"><a id="l01462" name="l01462"></a><span class="lineno"> 1462</span><span class="comment">   * Recall that an `ostream` manipulator is invoked in the style of `endl` and `flush`; for example: `cout &lt;&lt; endl;`.</span></div>
<div class="line"><a id="l01463" name="l01463"></a><span class="lineno"> 1463</span><span class="comment">   * It is atypical to call it directly as opposed to via the overloaded &quot;shift&quot; operator.</span></div>
<div class="line"><a id="l01464" name="l01464"></a><span class="lineno"> 1464</span><span class="comment">   *</span></div>
<div class="line"><a id="l01465" name="l01465"></a><span class="lineno"> 1465</span><span class="comment">   * Note that typically this is not invoked directly by the user but rather used in the `FLOW_LOG_...()` macros&#39;</span></div>
<div class="line"><a id="l01466" name="l01466"></a><span class="lineno"> 1466</span><span class="comment">   * implementation guts which is the original use case and hence reason for its existence.</span></div>
<div class="line"><a id="l01467" name="l01467"></a><span class="lineno"> 1467</span><span class="comment">   * However, there&#39;s no rule against direct uses, and it could prove useful at some point.  Any use beyond logging or</span></div>
<div class="line"><a id="l01468" name="l01468"></a><span class="lineno"> 1468</span><span class="comment">   * debugging is not recommended however (in particular, do not use to make any algorithmic decisions).</span></div>
<div class="line"><a id="l01469" name="l01469"></a><span class="lineno"> 1469</span><span class="comment">   *</span></div>
<div class="line"><a id="l01470" name="l01470"></a><span class="lineno"> 1470</span><span class="comment">   * This call is safe w/r/t concurrent execution with itself and this_thread_set_logged_nickname() in other</span></div>
<div class="line"><a id="l01471" name="l01471"></a><span class="lineno"> 1471</span><span class="comment">   * thread(s).</span></div>
<div class="line"><a id="l01472" name="l01472"></a><span class="lineno"> 1472</span><span class="comment">   *</span></div>
<div class="line"><a id="l01473" name="l01473"></a><span class="lineno"> 1473</span><span class="comment">   * @param os</span></div>
<div class="line"><a id="l01474" name="l01474"></a><span class="lineno"> 1474</span><span class="comment">   *        Stream to which to write thread&#39;s name.</span></div>
<div class="line"><a id="l01475" name="l01475"></a><span class="lineno"> 1475</span><span class="comment">   * @return `os`.</span></div>
<div class="line"><a id="l01476" name="l01476"></a><span class="lineno"> 1476</span><span class="comment">   */</span></div>
<div class="line"><a id="l01477" name="l01477"></a><span class="lineno"> 1477</span>  <span class="keyword">static</span> std::ostream&amp; <a class="code hl_function" href="classflow_1_1log_1_1Logger.html#a93541a6407b8705a76c7a161c5289b10">this_thread_logged_name_os_manip</a>(std::ostream&amp; os);</div>
<div class="line"><a id="l01478" name="l01478"></a><span class="lineno"> 1478</span><span class="comment"></span> </div>
<div class="line"><a id="l01479" name="l01479"></a><span class="lineno"> 1479</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01480" name="l01480"></a><span class="lineno"> 1480</span><span class="comment">   * Loads `msg_metadata-&gt;m_call_thread_nickname` (if set) or else `msg_metadata-&gt;m_call_thread_id`, based</span></div>
<div class="line"><a id="l01481" name="l01481"></a><span class="lineno"> 1481</span><span class="comment">   * on whether/how this_thread_set_logged_nickname() was last called in the current thread.</span></div>
<div class="line"><a id="l01482" name="l01482"></a><span class="lineno"> 1482</span><span class="comment">   * The two members should be set to ther default-constructed values on entry to the present function.</span></div>
<div class="line"><a id="l01483" name="l01483"></a><span class="lineno"> 1483</span><span class="comment">   *</span></div>
<div class="line"><a id="l01484" name="l01484"></a><span class="lineno"> 1484</span><span class="comment">   * @todo It would be more consistent to rename set_thread_info_in_msg_metadata() to</span></div>
<div class="line"><a id="l01485" name="l01485"></a><span class="lineno"> 1485</span><span class="comment">   * this_thread_set_info_in_msg_metadata(), since it operates in thread-local fashion.</span></div>
<div class="line"><a id="l01486" name="l01486"></a><span class="lineno"> 1486</span><span class="comment">   * This was a naming convention oversight.</span></div>
<div class="line"><a id="l01487" name="l01487"></a><span class="lineno"> 1487</span><span class="comment">   *</span></div>
<div class="line"><a id="l01488" name="l01488"></a><span class="lineno"> 1488</span><span class="comment">   * @param msg_metadata</span></div>
<div class="line"><a id="l01489" name="l01489"></a><span class="lineno"> 1489</span><span class="comment">   *        Non-null pointer to structure to modify.  See above.</span></div>
<div class="line"><a id="l01490" name="l01490"></a><span class="lineno"> 1490</span><span class="comment">   */</span></div>
<div class="line"><a id="l01491" name="l01491"></a><span class="lineno"> 1491</span>  <span class="keyword">static</span> <span class="keywordtype">void</span> <a class="code hl_function" href="classflow_1_1log_1_1Logger.html#a2d1a0283764e5f85abf00c7cee4c4e19">set_thread_info_in_msg_metadata</a>(<a class="code hl_struct" href="structflow_1_1log_1_1Msg__metadata.html">Msg_metadata</a>* msg_metadata);</div>
<div class="line"><a id="l01492" name="l01492"></a><span class="lineno"> 1492</span><span class="comment"></span> </div>
<div class="line"><a id="l01493" name="l01493"></a><span class="lineno"> 1493</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01494" name="l01494"></a><span class="lineno"> 1494</span><span class="comment">   * Same as set_thread_info_in_msg_metadata() but targets the given two variables as opposed to a</span></div>
<div class="line"><a id="l01495" name="l01495"></a><span class="lineno"> 1495</span><span class="comment">   * Msg_metadata.</span></div>
<div class="line"><a id="l01496" name="l01496"></a><span class="lineno"> 1496</span><span class="comment">   *</span></div>
<div class="line"><a id="l01497" name="l01497"></a><span class="lineno"> 1497</span><span class="comment">   * @todo It would be more consistent to rename set_thread_info() to</span></div>
<div class="line"><a id="l01498" name="l01498"></a><span class="lineno"> 1498</span><span class="comment">   * this_thread_set_info(), since it operates in thread-local fashion.</span></div>
<div class="line"><a id="l01499" name="l01499"></a><span class="lineno"> 1499</span><span class="comment">   * This was a naming convention oversight.</span></div>
<div class="line"><a id="l01500" name="l01500"></a><span class="lineno"> 1500</span><span class="comment">   *</span></div>
<div class="line"><a id="l01501" name="l01501"></a><span class="lineno"> 1501</span><span class="comment">   * @param call_thread_nickname</span></div>
<div class="line"><a id="l01502" name="l01502"></a><span class="lineno"> 1502</span><span class="comment">   *        Non-null pointer to value to modify.  See above.</span></div>
<div class="line"><a id="l01503" name="l01503"></a><span class="lineno"> 1503</span><span class="comment">   * @param call_thread_id</span></div>
<div class="line"><a id="l01504" name="l01504"></a><span class="lineno"> 1504</span><span class="comment">   *        Non-null pointer to value to modify.  See above.</span></div>
<div class="line"><a id="l01505" name="l01505"></a><span class="lineno"> 1505</span><span class="comment">   */</span></div>
<div class="line"><a id="l01506" name="l01506"></a><span class="lineno"> 1506</span>  <span class="keyword">static</span> <span class="keywordtype">void</span> <a class="code hl_function" href="classflow_1_1log_1_1Logger.html#a1ea9da10a13d3b422ba7162a13d7eeb1">set_thread_info</a>(std::string* call_thread_nickname,</div>
<div class="line"><a id="l01507" name="l01507"></a><span class="lineno"> 1507</span>                              <a class="code hl_typedef" href="namespaceflow_1_1util.html#a0a4e7b2d3107bd630e0dc0c0b8f2e4de">flow::util::Thread_id</a>* call_thread_id);</div>
<div class="line"><a id="l01508" name="l01508"></a><span class="lineno"> 1508</span><span class="comment"></span> </div>
<div class="line"><a id="l01509" name="l01509"></a><span class="lineno"> 1509</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01510" name="l01510"></a><span class="lineno"> 1510</span><span class="comment">   * Returns the stream dedicated to the executing thread and `this` Logger, so that the caller can apply</span></div>
<div class="line"><a id="l01511" name="l01511"></a><span class="lineno"> 1511</span><span class="comment">   * state-setting formatters to it.  If you write characters to it, or otherwise do anything othen than set</span></div>
<div class="line"><a id="l01512" name="l01512"></a><span class="lineno"> 1512</span><span class="comment">   * formatting state, or try to affect buffering behavior, behavior is undefined.  Usage example:</span></div>
<div class="line"><a id="l01513" name="l01513"></a><span class="lineno"> 1513</span><span class="comment">   *</span></div>
<div class="line"><a id="l01514" name="l01514"></a><span class="lineno"> 1514</span><span class="comment">   *   ~~~</span></div>
<div class="line"><a id="l01515" name="l01515"></a><span class="lineno"> 1515</span><span class="comment">   *   get_logger()-&gt;this_thread_ostream()-&gt;setf(std::fixed | std::right);</span></div>
<div class="line"><a id="l01516" name="l01516"></a><span class="lineno"> 1516</span><span class="comment">   *   *(get_logger()-&gt;this_thread_ostream()) &lt;&lt; std::setw(2);</span></div>
<div class="line"><a id="l01517" name="l01517"></a><span class="lineno"> 1517</span><span class="comment">   *   // *get_logger()&#39;s subsequent messages (such as the following) from the current thread will use above formatting.</span></div>
<div class="line"><a id="l01518" name="l01518"></a><span class="lineno"> 1518</span><span class="comment">   *   FLOW_LOG_WARNING(&quot;Let&#39;s print a number with some formatting: &quot; &lt;&lt; 0.5);</span></div>
<div class="line"><a id="l01519" name="l01519"></a><span class="lineno"> 1519</span><span class="comment">   *   ~~~</span></div>
<div class="line"><a id="l01520" name="l01520"></a><span class="lineno"> 1520</span><span class="comment">   *</span></div>
<div class="line"><a id="l01521" name="l01521"></a><span class="lineno"> 1521</span><span class="comment">   * Note that you could just as well apply the intended formatters via regular log statements.</span></div>
<div class="line"><a id="l01522" name="l01522"></a><span class="lineno"> 1522</span><span class="comment">   * However, there are disadvantages to that approach -- but they do not always apply.  The disadvantages are listed</span></div>
<div class="line"><a id="l01523" name="l01523"></a><span class="lineno"> 1523</span><span class="comment">   * below; but the short version is you should typically use the present method if and only if you are attempting to</span></div>
<div class="line"><a id="l01524" name="l01524"></a><span class="lineno"> 1524</span><span class="comment">   * affect subsequent logging at large, not a particular fragment of a particular message.</span></div>
<div class="line"><a id="l01525" name="l01525"></a><span class="lineno"> 1525</span><span class="comment">   *</span></div>
<div class="line"><a id="l01526" name="l01526"></a><span class="lineno"> 1526</span><span class="comment">   * Formally, the disadvantages of affecting formatting state of the underlying stream via log macros:</span></div>
<div class="line"><a id="l01527" name="l01527"></a><span class="lineno"> 1527</span><span class="comment">   * - If the log statement is ignored due to failing a filter check,</span></div>
<div class="line"><a id="l01528" name="l01528"></a><span class="lineno"> 1528</span><span class="comment">   *   then any formatters therein will also be ignored.  (However, you could use a macro that bypasses such a check.</span></div>
<div class="line"><a id="l01529" name="l01529"></a><span class="lineno"> 1529</span><span class="comment">   *   On the other hand, stylistically one would typically only do that after checking the severity manually</span></div>
<div class="line"><a id="l01530" name="l01530"></a><span class="lineno"> 1530</span><span class="comment">   *   for performance of combining several log statements with equal severities.  Using it *just* to apply formatters</span></div>
<div class="line"><a id="l01531" name="l01531"></a><span class="lineno"> 1531</span><span class="comment">   *   is stylistically dubious.)</span></div>
<div class="line"><a id="l01532" name="l01532"></a><span class="lineno"> 1532</span><span class="comment">   * - If you are trying to affect subsequent logging at large, you&#39;d hypothetically use something like</span></div>
<div class="line"><a id="l01533" name="l01533"></a><span class="lineno"> 1533</span><span class="comment">   *   `FLOW_LOG_INFO_WITHOUT_CHECKING(...formatter... &lt;&lt; ...formatter... &lt;&lt; ...);`.  This is stylistically dubious,</span></div>
<div class="line"><a id="l01534" name="l01534"></a><span class="lineno"> 1534</span><span class="comment">   *   because the lack of characters being output means the severity (INFO in this case) is disregarded and is</span></div>
<div class="line"><a id="l01535" name="l01535"></a><span class="lineno"> 1535</span><span class="comment">   *   a dummy value.</span></div>
<div class="line"><a id="l01536" name="l01536"></a><span class="lineno"> 1536</span><span class="comment">   * - While one can pass many formatters as `&lt;&lt;` operator arguments, there are others than do not use that syntax.</span></div>
<div class="line"><a id="l01537" name="l01537"></a><span class="lineno"> 1537</span><span class="comment">   *   For example, `ostream::setf()` is a method *of* `std::ostream`.  Thus the log macros do not help.</span></div>
<div class="line"><a id="l01538" name="l01538"></a><span class="lineno"> 1538</span><span class="comment">   *</span></div>
<div class="line"><a id="l01539" name="l01539"></a><span class="lineno"> 1539</span><span class="comment">   * Recall that the stream involved is completely orthogonal to any underlying stream that may be ultimately output</span></div>
<div class="line"><a id="l01540" name="l01540"></a><span class="lineno"> 1540</span><span class="comment">   * to by Logger for the actual, ultimate output of characters.  E.g., if Logger happens to be Simple_ostream_logger</span></div>
<div class="line"><a id="l01541" name="l01541"></a><span class="lineno"> 1541</span><span class="comment">   * targeted at `std::cout`, the above snippet would in no way touch `std::cout` formatting.  In fact, Logger may</span></div>
<div class="line"><a id="l01542" name="l01542"></a><span class="lineno"> 1542</span><span class="comment">   * not even use streams for output; that is an orthogonal implementation detail.</span></div>
<div class="line"><a id="l01543" name="l01543"></a><span class="lineno"> 1543</span><span class="comment">   *</span></div>
<div class="line"><a id="l01544" name="l01544"></a><span class="lineno"> 1544</span><span class="comment">   * @return Pointer to stream; always the same value for a given thread and different among all distinct threads.</span></div>
<div class="line"><a id="l01545" name="l01545"></a><span class="lineno"> 1545</span><span class="comment">   */</span></div>
<div class="line"><a id="l01546" name="l01546"></a><span class="lineno"> 1546</span>  std::ostream* <a class="code hl_function" href="classflow_1_1log_1_1Logger.html#ad6ead44c19a7b15111b2f77656a2ea31">this_thread_ostream</a>() <span class="keyword">const</span>;</div>
<div class="line"><a id="l01547" name="l01547"></a><span class="lineno"> 1547</span> </div>
<div class="line"><a id="l01548" name="l01548"></a><span class="lineno"> 1548</span><span class="keyword">private</span>:</div>
<div class="line"><a id="l01549" name="l01549"></a><span class="lineno"> 1549</span>  <span class="comment">// Data.</span></div>
<div class="line"><a id="l01550" name="l01550"></a><span class="lineno"> 1550</span><span class="comment"></span> </div>
<div class="line"><a id="l01551" name="l01551"></a><span class="lineno"> 1551</span><span class="comment">  /// Thread-local storage for each thread&#39;s logged name (null pointer, which is default, means no nickname stored).</span></div>
<div class="line"><a id="l01552" name="l01552"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Logger.html#a3e00a68f9086f1ef0f4e36b9f23f4d02"> 1552</a></span><span class="comment"></span>  <span class="keyword">static</span> boost::thread_specific_ptr&lt;std::string&gt; <a class="code hl_variable" href="classflow_1_1log_1_1Logger.html#a3e00a68f9086f1ef0f4e36b9f23f4d02">s_this_thread_nickname_ptr</a>;</div>
<div class="line"><a id="l01553" name="l01553"></a><span class="lineno"> 1553</span>}; <span class="comment">// class Logger</span></div>
<div class="line"><a id="l01554" name="l01554"></a><span class="lineno"> 1554</span><span class="comment"></span> </div>
<div class="line"><a id="l01555" name="l01555"></a><span class="lineno"> 1555</span><span class="comment">/**</span></div>
<div class="line"><a id="l01556" name="l01556"></a><span class="lineno"> 1556</span><span class="comment"> * Convenience class that simply stores a Logger and/or Component passed into a constructor; and returns this</span></div>
<div class="line"><a id="l01557" name="l01557"></a><span class="lineno"> 1557</span><span class="comment"> * Logger and Component via get_logger() and get_log_component() public accessors.  It&#39;s extremely</span></div>
<div class="line"><a id="l01558" name="l01558"></a><span class="lineno"> 1558</span><span class="comment"> * useful (almost mandatory in conventional practice) for classes that want to log, as they can simply</span></div>
<div class="line"><a id="l01559" name="l01559"></a><span class="lineno"> 1559</span><span class="comment"> * derive from it (passing in the desired `Logger*` and Component payload (an `enum`</span></div>
<div class="line"><a id="l01560" name="l01560"></a><span class="lineno"> 1560</span><span class="comment"> * value) into the Log_context superclass constructor),</span></div>
<div class="line"><a id="l01561" name="l01561"></a><span class="lineno"> 1561</span><span class="comment"> * at which point the get_logger() and get_log_component() functions the `FLOW_LOG_...()` macros expect automatically</span></div>
<div class="line"><a id="l01562" name="l01562"></a><span class="lineno"> 1562</span><span class="comment"> * become available without any additional code having to be written in the logging class.  Here is how:</span></div>
<div class="line"><a id="l01563" name="l01563"></a><span class="lineno"> 1563</span><span class="comment"> *</span></div>
<div class="line"><a id="l01564" name="l01564"></a><span class="lineno"> 1564</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l01565" name="l01565"></a><span class="lineno"> 1565</span><span class="comment"> *   class I_like_to_have_fun_and_log_about_it :</span></div>
<div class="line"><a id="l01566" name="l01566"></a><span class="lineno"> 1566</span><span class="comment"> *     public flow::log::Log_context</span></div>
<div class="line"><a id="l01567" name="l01567"></a><span class="lineno"> 1567</span><span class="comment"> *   {</span></div>
<div class="line"><a id="l01568" name="l01568"></a><span class="lineno"> 1568</span><span class="comment"> *   public:</span></div>
<div class="line"><a id="l01569" name="l01569"></a><span class="lineno"> 1569</span><span class="comment"> *     I_like_to_have_fun_and_log_about_it() :</span></div>
<div class="line"><a id="l01570" name="l01570"></a><span class="lineno"> 1570</span><span class="comment"> *       // Glue FLOW_LOG_*() macros to the following simple logger and component FUN_HAVER.</span></div>
<div class="line"><a id="l01571" name="l01571"></a><span class="lineno"> 1571</span><span class="comment"> *       Log_context(&amp;m_logger, My_cool_components::S_FUN_HAVER),</span></div>
<div class="line"><a id="l01572" name="l01572"></a><span class="lineno"> 1572</span><span class="comment"> *       // Initialize stdout logger that logs INFO-or-higher-severity messages.</span></div>
<div class="line"><a id="l01573" name="l01573"></a><span class="lineno"> 1573</span><span class="comment"> *       m_logger(true, std::cout, std::cout, flow::log::Sev::S_INFO),</span></div>
<div class="line"><a id="l01574" name="l01574"></a><span class="lineno"> 1574</span><span class="comment"> *       // ... other initializers and superclass constructors, if any ...</span></div>
<div class="line"><a id="l01575" name="l01575"></a><span class="lineno"> 1575</span><span class="comment"> *     {</span></div>
<div class="line"><a id="l01576" name="l01576"></a><span class="lineno"> 1576</span><span class="comment"> *       FLOW_LOG_INFO(&quot;I can log right from the constructor and throughout *this lifetime!&quot;);</span></div>
<div class="line"><a id="l01577" name="l01577"></a><span class="lineno"> 1577</span><span class="comment"> *       // ... other code ...</span></div>
<div class="line"><a id="l01578" name="l01578"></a><span class="lineno"> 1578</span><span class="comment"> *     }</span></div>
<div class="line"><a id="l01579" name="l01579"></a><span class="lineno"> 1579</span><span class="comment"> *</span></div>
<div class="line"><a id="l01580" name="l01580"></a><span class="lineno"> 1580</span><span class="comment"> *   private:</span></div>
<div class="line"><a id="l01581" name="l01581"></a><span class="lineno"> 1581</span><span class="comment"> *     void do_fun_stuff()</span></div>
<div class="line"><a id="l01582" name="l01582"></a><span class="lineno"> 1582</span><span class="comment"> *     {</span></div>
<div class="line"><a id="l01583" name="l01583"></a><span class="lineno"> 1583</span><span class="comment"> *       // This macro works, because Log_context superclass defines get_logger() which returns m_logger,</span></div>
<div class="line"><a id="l01584" name="l01584"></a><span class="lineno"> 1584</span><span class="comment"> *       // and component() returns My_cool_components::S_FUN_HAVER.</span></div>
<div class="line"><a id="l01585" name="l01585"></a><span class="lineno"> 1585</span><span class="comment"> *       // But we need not ever worry about such details.</span></div>
<div class="line"><a id="l01586" name="l01586"></a><span class="lineno"> 1586</span><span class="comment"> *       FLOW_LOG_INFO(&quot;I am about to do something cool and fun: &quot; &lt;&lt; 42 &lt;&lt; &quot;!&quot;);</span></div>
<div class="line"><a id="l01587" name="l01587"></a><span class="lineno"> 1587</span><span class="comment"> *       // ... more code ...</span></div>
<div class="line"><a id="l01588" name="l01588"></a><span class="lineno"> 1588</span><span class="comment"> *     }</span></div>
<div class="line"><a id="l01589" name="l01589"></a><span class="lineno"> 1589</span><span class="comment"> *</span></div>
<div class="line"><a id="l01590" name="l01590"></a><span class="lineno"> 1590</span><span class="comment"> *     // I will use a simple stdout/stderr logger for my logging. It&#39;s passed to Log_context in constructor.</span></div>
<div class="line"><a id="l01591" name="l01591"></a><span class="lineno"> 1591</span><span class="comment"> *     flow::log::Simple_ostream_logger m_logger;</span></div>
<div class="line"><a id="l01592" name="l01592"></a><span class="lineno"> 1592</span><span class="comment"> *   }; // class I_like_to_have_fun_and_log_about_it</span></div>
<div class="line"><a id="l01593" name="l01593"></a><span class="lineno"> 1593</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l01594" name="l01594"></a><span class="lineno"> 1594</span><span class="comment"> *</span></div>
<div class="line"><a id="l01595" name="l01595"></a><span class="lineno"> 1595</span><span class="comment"> * Note that the `operator=()` allows one to change the underlying Logger anytime after</span></div>
<div class="line"><a id="l01596" name="l01596"></a><span class="lineno"> 1596</span><span class="comment"> * construction (e.g., `existing_log_context = Log_context(&amp;some_logger, Some_enum::S_SOME_COMPONENT);`).</span></div>
<div class="line"><a id="l01597" name="l01597"></a><span class="lineno"> 1597</span><span class="comment"> *</span></div>
<div class="line"><a id="l01598" name="l01598"></a><span class="lineno"> 1598</span><span class="comment"> * ### Implementation notes ###</span></div>
<div class="line"><a id="l01599" name="l01599"></a><span class="lineno"> 1599</span><span class="comment"> * The code could be shorter by getting rid of non-copy constuctor in favor of direct member initialization by user;</span></div>
<div class="line"><a id="l01600" name="l01600"></a><span class="lineno"> 1600</span><span class="comment"> * and by simply omitting the API for the auto-generated copy constructor and assignment.  However, in this case,</span></div>
<div class="line"><a id="l01601" name="l01601"></a><span class="lineno"> 1601</span><span class="comment"> * I wanted to clearly document the API; and since there are more than 1 constructors, it seemed better to explicitly</span></div>
<div class="line"><a id="l01602" name="l01602"></a><span class="lineno"> 1602</span><span class="comment"> * declare them all instead of replacing some with implicitly required direct initialization (again to make API more</span></div>
<div class="line"><a id="l01603" name="l01603"></a><span class="lineno"> 1603</span><span class="comment"> * clearly documented).</span></div>
<div class="line"><a id="l01604" name="l01604"></a><span class="lineno"> 1604</span><span class="comment"> *</span></div>
<div class="line"><a id="l01605" name="l01605"></a><span class="lineno"> 1605</span><span class="comment"> * ### Thread safety ###</span></div>
<div class="line"><a id="l01606" name="l01606"></a><span class="lineno"> 1606</span><span class="comment"> * The only operation of interest w/r/t threads is the aforementioned implicit assignment operator.  Thread safety is</span></div>
<div class="line"><a id="l01607" name="l01607"></a><span class="lineno"> 1607</span><span class="comment"> * the same as for any `struct` with no locking done therein.</span></div>
<div class="line"><a id="l01608" name="l01608"></a><span class="lineno"> 1608</span><span class="comment"> */</span></div>
<div class="line"><a id="l01609" name="l01609"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Log__context.html"> 1609</a></span><span class="keyword">class </span><a class="code hl_class" href="classflow_1_1log_1_1Log__context.html">Log_context</a></div>
<div class="line"><a id="l01610" name="l01610"></a><span class="lineno"> 1610</span>{</div>
<div class="line"><a id="l01611" name="l01611"></a><span class="lineno"> 1611</span><span class="keyword">public</span>:</div>
<div class="line"><a id="l01612" name="l01612"></a><span class="lineno"> 1612</span>  <span class="comment">// Constructors/destructor.</span></div>
<div class="line"><a id="l01613" name="l01613"></a><span class="lineno"> 1613</span><span class="comment"></span> </div>
<div class="line"><a id="l01614" name="l01614"></a><span class="lineno"> 1614</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01615" name="l01615"></a><span class="lineno"> 1615</span><span class="comment">   * Constructs Log_context by storing the given pointer to a Logger and a null Component.</span></div>
<div class="line"><a id="l01616" name="l01616"></a><span class="lineno"> 1616</span><span class="comment">   *</span></div>
<div class="line"><a id="l01617" name="l01617"></a><span class="lineno"> 1617</span><span class="comment">   * @param logger</span></div>
<div class="line"><a id="l01618" name="l01618"></a><span class="lineno"> 1618</span><span class="comment">   *        Pointer to store.  Rationale for providing the null default: To facilitate subclass `= default` no-arg</span></div>
<div class="line"><a id="l01619" name="l01619"></a><span class="lineno"> 1619</span><span class="comment">   *        ctors.</span></div>
<div class="line"><a id="l01620" name="l01620"></a><span class="lineno"> 1620</span><span class="comment">   */</span></div>
<div class="line"><a id="l01621" name="l01621"></a><span class="lineno"> 1621</span>  <span class="keyword">explicit</span> <a class="code hl_function" href="classflow_1_1log_1_1Log__context.html#ae7100d2dd130d8f130e3e64fdb1f4fd9">Log_context</a>(<a class="code hl_class" href="classflow_1_1log_1_1Logger.html">Logger</a>* logger = 0);</div>
<div class="line"><a id="l01622" name="l01622"></a><span class="lineno"> 1622</span><span class="comment"></span> </div>
<div class="line"><a id="l01623" name="l01623"></a><span class="lineno"> 1623</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01624" name="l01624"></a><span class="lineno"> 1624</span><span class="comment">   * Constructs Log_context by storing the given pointer to a Logger and a new Component storing the</span></div>
<div class="line"><a id="l01625" name="l01625"></a><span class="lineno"> 1625</span><span class="comment">   * specified generically typed payload (an `enum` value).  For more background on Component see its</span></div>
<div class="line"><a id="l01626" name="l01626"></a><span class="lineno"> 1626</span><span class="comment">   * doc header.</span></div>
<div class="line"><a id="l01627" name="l01627"></a><span class="lineno"> 1627</span><span class="comment">   *</span></div>
<div class="line"><a id="l01628" name="l01628"></a><span class="lineno"> 1628</span><span class="comment">   * @tparam Component_payload</span></div>
<div class="line"><a id="l01629" name="l01629"></a><span class="lineno"> 1629</span><span class="comment">   *         See Component constructor doc header: `Payload` template arg specifically.</span></div>
<div class="line"><a id="l01630" name="l01630"></a><span class="lineno"> 1630</span><span class="comment">   * @param logger</span></div>
<div class="line"><a id="l01631" name="l01631"></a><span class="lineno"> 1631</span><span class="comment">   *        Pointer to store.</span></div>
<div class="line"><a id="l01632" name="l01632"></a><span class="lineno"> 1632</span><span class="comment">   * @param component_payload</span></div>
<div class="line"><a id="l01633" name="l01633"></a><span class="lineno"> 1633</span><span class="comment">   *        See Component constructor doc header: `payload` arg specifically.</span></div>
<div class="line"><a id="l01634" name="l01634"></a><span class="lineno"> 1634</span><span class="comment">   */</span></div>
<div class="line"><a id="l01635" name="l01635"></a><span class="lineno"> 1635</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> Component_payload&gt;</div>
<div class="line"><a id="l01636" name="l01636"></a><span class="lineno"> 1636</span>  <span class="keyword">explicit</span> <a class="code hl_function" href="classflow_1_1log_1_1Log__context.html#ae7100d2dd130d8f130e3e64fdb1f4fd9">Log_context</a>(<a class="code hl_class" href="classflow_1_1log_1_1Logger.html">Logger</a>* logger, Component_payload component_payload);</div>
<div class="line"><a id="l01637" name="l01637"></a><span class="lineno"> 1637</span><span class="comment"></span> </div>
<div class="line"><a id="l01638" name="l01638"></a><span class="lineno"> 1638</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01639" name="l01639"></a><span class="lineno"> 1639</span><span class="comment">   * Copy constructor that stores equal `Logger*` and Component values as the source.</span></div>
<div class="line"><a id="l01640" name="l01640"></a><span class="lineno"> 1640</span><span class="comment">   *</span></div>
<div class="line"><a id="l01641" name="l01641"></a><span class="lineno"> 1641</span><span class="comment">   * This is `explicit`, even though an unintentional copy (e.g., in a `bind` sans `cref` or `ref`) would just</span></div>
<div class="line"><a id="l01642" name="l01642"></a><span class="lineno"> 1642</span><span class="comment">   * internally involve the copying a pointer (as of this writing).  The reason is that it&#39;s unlikely one wants</span></div>
<div class="line"><a id="l01643" name="l01643"></a><span class="lineno"> 1643</span><span class="comment">   * to blithely copy these objects or objects of a sub-type; most likely (at least in scenarios seen so far, as of</span></div>
<div class="line"><a id="l01644" name="l01644"></a><span class="lineno"> 1644</span><span class="comment">   * this writing) a `cref` or `ref` is in order instead.  (I am open to counter-examples and thus removing this</span></div>
<div class="line"><a id="l01645" name="l01645"></a><span class="lineno"> 1645</span><span class="comment">   * `explicit` keyword if convinced by one.)</span></div>
<div class="line"><a id="l01646" name="l01646"></a><span class="lineno"> 1646</span><span class="comment">   *</span></div>
<div class="line"><a id="l01647" name="l01647"></a><span class="lineno"> 1647</span><span class="comment">   * @param src</span></div>
<div class="line"><a id="l01648" name="l01648"></a><span class="lineno"> 1648</span><span class="comment">   *        Source object.</span></div>
<div class="line"><a id="l01649" name="l01649"></a><span class="lineno"> 1649</span><span class="comment">   */</span></div>
<div class="line"><a id="l01650" name="l01650"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Log__context.html#a5c57a7f44959a01ca9a1c948a6686cc0"> 1650</a></span>  <span class="keyword">explicit</span> <a class="code hl_function" href="classflow_1_1log_1_1Log__context.html#a5c57a7f44959a01ca9a1c948a6686cc0">Log_context</a>(<span class="keyword">const</span> <a class="code hl_class" href="classflow_1_1log_1_1Log__context.html">Log_context</a>&amp; src);</div>
<div class="line"><a id="l01651" name="l01651"></a><span class="lineno"> 1651</span><span class="comment"></span> </div>
<div class="line"><a id="l01652" name="l01652"></a><span class="lineno"> 1652</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01653" name="l01653"></a><span class="lineno"> 1653</span><span class="comment">   * Move constructor that makes this equal to `src`, while the latter becomes as-if default-constructed.</span></div>
<div class="line"><a id="l01654" name="l01654"></a><span class="lineno"> 1654</span><span class="comment">   *</span></div>
<div class="line"><a id="l01655" name="l01655"></a><span class="lineno"> 1655</span><span class="comment">   * @param src</span></div>
<div class="line"><a id="l01656" name="l01656"></a><span class="lineno"> 1656</span><span class="comment">   *        Source object.</span></div>
<div class="line"><a id="l01657" name="l01657"></a><span class="lineno"> 1657</span><span class="comment">   */</span></div>
<div class="line"><a id="l01658" name="l01658"></a><span class="lineno"> 1658</span>  <a class="code hl_function" href="classflow_1_1log_1_1Log__context.html#ae7100d2dd130d8f130e3e64fdb1f4fd9">Log_context</a>(<a class="code hl_class" href="classflow_1_1log_1_1Log__context.html">Log_context</a>&amp;&amp; src);</div>
<div class="line"><a id="l01659" name="l01659"></a><span class="lineno"> 1659</span> </div>
<div class="line"><a id="l01660" name="l01660"></a><span class="lineno"> 1660</span>  <span class="comment">// Methods.</span></div>
<div class="line"><a id="l01661" name="l01661"></a><span class="lineno"> 1661</span><span class="comment"></span> </div>
<div class="line"><a id="l01662" name="l01662"></a><span class="lineno"> 1662</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01663" name="l01663"></a><span class="lineno"> 1663</span><span class="comment">   * Assignment operator that behaves similarly to the copy constructor.</span></div>
<div class="line"><a id="l01664" name="l01664"></a><span class="lineno"> 1664</span><span class="comment">   *</span></div>
<div class="line"><a id="l01665" name="l01665"></a><span class="lineno"> 1665</span><span class="comment">   * @param src</span></div>
<div class="line"><a id="l01666" name="l01666"></a><span class="lineno"> 1666</span><span class="comment">   *        Source object.</span></div>
<div class="line"><a id="l01667" name="l01667"></a><span class="lineno"> 1667</span><span class="comment">   * @return `*this`.</span></div>
<div class="line"><a id="l01668" name="l01668"></a><span class="lineno"> 1668</span><span class="comment">   */</span></div>
<div class="line"><a id="l01669" name="l01669"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Log__context.html#a5d628315d5a93908d47a281980d3113e"> 1669</a></span>  <a class="code hl_class" href="classflow_1_1log_1_1Log__context.html">Log_context</a>&amp; <a class="code hl_function" href="classflow_1_1log_1_1Log__context.html#a5d628315d5a93908d47a281980d3113e">operator=</a>(<span class="keyword">const</span> <a class="code hl_class" href="classflow_1_1log_1_1Log__context.html">Log_context</a>&amp; src);</div>
<div class="line"><a id="l01670" name="l01670"></a><span class="lineno"> 1670</span><span class="comment"></span> </div>
<div class="line"><a id="l01671" name="l01671"></a><span class="lineno"> 1671</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01672" name="l01672"></a><span class="lineno"> 1672</span><span class="comment">   * Move assignment operator that behaves similarly to the move constructor.</span></div>
<div class="line"><a id="l01673" name="l01673"></a><span class="lineno"> 1673</span><span class="comment">   *</span></div>
<div class="line"><a id="l01674" name="l01674"></a><span class="lineno"> 1674</span><span class="comment">   * @param src</span></div>
<div class="line"><a id="l01675" name="l01675"></a><span class="lineno"> 1675</span><span class="comment">   *        Source object.</span></div>
<div class="line"><a id="l01676" name="l01676"></a><span class="lineno"> 1676</span><span class="comment">   * @return `*this`.</span></div>
<div class="line"><a id="l01677" name="l01677"></a><span class="lineno"> 1677</span><span class="comment">   */</span></div>
<div class="line"><a id="l01678" name="l01678"></a><span class="lineno"> 1678</span>  <a class="code hl_class" href="classflow_1_1log_1_1Log__context.html">Log_context</a>&amp; <a class="code hl_function" href="classflow_1_1log_1_1Log__context.html#a5d628315d5a93908d47a281980d3113e">operator=</a>(<a class="code hl_class" href="classflow_1_1log_1_1Log__context.html">Log_context</a>&amp;&amp; src);</div>
<div class="line"><a id="l01679" name="l01679"></a><span class="lineno"> 1679</span><span class="comment"></span> </div>
<div class="line"><a id="l01680" name="l01680"></a><span class="lineno"> 1680</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01681" name="l01681"></a><span class="lineno"> 1681</span><span class="comment">   * Swaps Logger pointers and Component objects held by `*this` and `other`.  No-op if `this == &amp;other`.</span></div>
<div class="line"><a id="l01682" name="l01682"></a><span class="lineno"> 1682</span><span class="comment">   *</span></div>
<div class="line"><a id="l01683" name="l01683"></a><span class="lineno"> 1683</span><span class="comment">   * @param other</span></div>
<div class="line"><a id="l01684" name="l01684"></a><span class="lineno"> 1684</span><span class="comment">   *        Other object.</span></div>
<div class="line"><a id="l01685" name="l01685"></a><span class="lineno"> 1685</span><span class="comment">   */</span></div>
<div class="line"><a id="l01686" name="l01686"></a><span class="lineno"> 1686</span>  <span class="keywordtype">void</span> <a class="code hl_function" href="classflow_1_1log_1_1Log__context.html#aa6bb8e4250586425631ef80063caf155">swap</a>(<a class="code hl_class" href="classflow_1_1log_1_1Log__context.html">Log_context</a>&amp; other);</div>
<div class="line"><a id="l01687" name="l01687"></a><span class="lineno"> 1687</span><span class="comment"></span> </div>
<div class="line"><a id="l01688" name="l01688"></a><span class="lineno"> 1688</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01689" name="l01689"></a><span class="lineno"> 1689</span><span class="comment">   * Returns the stored Logger pointer, particularly as many `FLOW_LOG_*()` macros expect.</span></div>
<div class="line"><a id="l01690" name="l01690"></a><span class="lineno"> 1690</span><span class="comment">   *</span></div>
<div class="line"><a id="l01691" name="l01691"></a><span class="lineno"> 1691</span><span class="comment">   * @note It&#39;s public at least so that FLOW_LOG_SET_CONTEXT() works in all reasonable contexts.</span></div>
<div class="line"><a id="l01692" name="l01692"></a><span class="lineno"> 1692</span><span class="comment">   *</span></div>
<div class="line"><a id="l01693" name="l01693"></a><span class="lineno"> 1693</span><span class="comment">   * @return See above.</span></div>
<div class="line"><a id="l01694" name="l01694"></a><span class="lineno"> 1694</span><span class="comment">   */</span></div>
<div class="line"><a id="l01695" name="l01695"></a><span class="lineno"> 1695</span>  <a class="code hl_class" href="classflow_1_1log_1_1Logger.html">Logger</a>* <a class="code hl_function" href="classflow_1_1log_1_1Log__context.html#af4db395042b065b00398cd59845dcb4d">get_logger</a>() <span class="keyword">const</span>;</div>
<div class="line"><a id="l01696" name="l01696"></a><span class="lineno"> 1696</span><span class="comment"></span> </div>
<div class="line"><a id="l01697" name="l01697"></a><span class="lineno"> 1697</span><span class="comment">  /**</span></div>
<div class="line"><a id="l01698" name="l01698"></a><span class="lineno"> 1698</span><span class="comment">   * Returns reference to the stored Component object, particularly as many `FLOW_LOG_*()` macros expect.</span></div>
<div class="line"><a id="l01699" name="l01699"></a><span class="lineno"> 1699</span><span class="comment">   *</span></div>
<div class="line"><a id="l01700" name="l01700"></a><span class="lineno"> 1700</span><span class="comment">   * @note It&#39;s public at least so that FLOW_LOG_SET_CONTEXT() works in all reasonable contexts.</span></div>
<div class="line"><a id="l01701" name="l01701"></a><span class="lineno"> 1701</span><span class="comment">   *</span></div>
<div class="line"><a id="l01702" name="l01702"></a><span class="lineno"> 1702</span><span class="comment">   * @return See above.</span></div>
<div class="line"><a id="l01703" name="l01703"></a><span class="lineno"> 1703</span><span class="comment">   */</span></div>
<div class="line"><a id="l01704" name="l01704"></a><span class="lineno"> 1704</span>  <span class="keyword">const</span> <a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a>&amp; <a class="code hl_function" href="classflow_1_1log_1_1Log__context.html#a8a5fef42dc2cedf3c0d1a6e83beb2948">get_log_component</a>() <span class="keyword">const</span>;</div>
<div class="line"><a id="l01705" name="l01705"></a><span class="lineno"> 1705</span> </div>
<div class="line"><a id="l01706" name="l01706"></a><span class="lineno"> 1706</span><span class="keyword">private</span>:</div>
<div class="line"><a id="l01707" name="l01707"></a><span class="lineno"> 1707</span>  <span class="comment">// Data.</span></div>
<div class="line"><a id="l01708" name="l01708"></a><span class="lineno"> 1708</span><span class="comment"></span> </div>
<div class="line"><a id="l01709" name="l01709"></a><span class="lineno"> 1709</span><span class="comment">  /// The held Logger pointer.  Making the pointer itself non-`const` to allow `operator=()` to work.</span></div>
<div class="line"><a id="l01710" name="l01710"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Log__context.html#af13297446a54d6d80eb33d8fc672c10f"> 1710</a></span><span class="comment"></span>  <a class="code hl_class" href="classflow_1_1log_1_1Logger.html">Logger</a>* <a class="code hl_variable" href="classflow_1_1log_1_1Log__context.html#af13297446a54d6d80eb33d8fc672c10f">m_logger</a>;<span class="comment"></span></div>
<div class="line"><a id="l01711" name="l01711"></a><span class="lineno"> 1711</span><span class="comment">  /// The held Component object.  Making the object non-`const` to allow `operator=()` to work.</span></div>
<div class="line"><a id="l01712" name="l01712"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Log__context.html#acf51230f139ac6f17748a02111b04086"> 1712</a></span><span class="comment"></span>  <a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a> <a class="code hl_variable" href="classflow_1_1log_1_1Log__context.html#acf51230f139ac6f17748a02111b04086">m_component</a>;</div>
<div class="line"><a id="l01713" name="l01713"></a><span class="lineno"> 1713</span>}; <span class="comment">// class Log_context</span></div>
<div class="line"><a id="l01714" name="l01714"></a><span class="lineno"> 1714</span> </div>
<div class="line"><a id="l01715" name="l01715"></a><span class="lineno"> 1715</span><span class="comment">// Free functions: in *_fwd.hpp.</span></div>
<div class="line"><a id="l01716" name="l01716"></a><span class="lineno"> 1716</span> </div>
<div class="line"><a id="l01717" name="l01717"></a><span class="lineno"> 1717</span><span class="comment">// Template implementations.</span></div>
<div class="line"><a id="l01718" name="l01718"></a><span class="lineno"> 1718</span> </div>
<div class="line"><a id="l01719" name="l01719"></a><span class="lineno"> 1719</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> Payload&gt;</div>
<div class="line"><a id="l01720" name="l01720"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Component.html#a2dbca7a7e6b6c43c2119db1858c3b29d"> 1720</a></span><a class="code hl_function" href="classflow_1_1log_1_1Component.html#a8c746035d0eea4a26d0982eabf63b713">Component::Component</a>(Payload payload)</div>
<div class="line"><a id="l01721" name="l01721"></a><span class="lineno"> 1721</span>{</div>
<div class="line"><a id="l01722" name="l01722"></a><span class="lineno"> 1722</span>  <span class="comment">// Currently uninitialized.  Now:</span></div>
<div class="line"><a id="l01723" name="l01723"></a><span class="lineno"> 1723</span>  <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a146ce02cc7422b3a3bca07533536450e">operator=</a>(<a class="code hl_function" href="classflow_1_1log_1_1Component.html#a656f5868adbd8c58c493981fe1764699">payload</a>);</div>
<div class="line"><a id="l01724" name="l01724"></a><span class="lineno"> 1724</span>}</div>
<div class="line"><a id="l01725" name="l01725"></a><span class="lineno"> 1725</span> </div>
<div class="line"><a id="l01726" name="l01726"></a><span class="lineno"> 1726</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> Payload&gt;</div>
<div class="line"><a id="l01727" name="l01727"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Component.html#a656f5868adbd8c58c493981fe1764699"> 1727</a></span>Payload <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a656f5868adbd8c58c493981fe1764699">Component::payload</a>()<span class="keyword"> const</span></div>
<div class="line"><a id="l01728" name="l01728"></a><span class="lineno"> 1728</span><span class="keyword"></span>{</div>
<div class="line"><a id="l01729" name="l01729"></a><span class="lineno"> 1729</span>  <span class="comment">// Zero processor cycles (an `enum` value *is* internally its integer value).</span></div>
<div class="line"><a id="l01730" name="l01730"></a><span class="lineno"> 1730</span>  <span class="keywordflow">return</span> <span class="keyword">static_cast&lt;</span>Payload<span class="keyword">&gt;</span>(<a class="code hl_variable" href="classflow_1_1log_1_1Component.html#a5be216ad60f3e344a22151bdf4d8d8b6">m_payload_enum_raw_value</a>);</div>
<div class="line"><a id="l01731" name="l01731"></a><span class="lineno"> 1731</span>}</div>
<div class="line"><a id="l01732" name="l01732"></a><span class="lineno"> 1732</span> </div>
<div class="line"><a id="l01733" name="l01733"></a><span class="lineno"> 1733</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> Payload&gt;</div>
<div class="line"><a id="l01734" name="l01734"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Component.html#ae0587562779694526b8dd1e8f7012494"> 1734</a></span><a class="code hl_class" href="classflow_1_1log_1_1Component.html">Component</a>&amp; <a class="code hl_function" href="classflow_1_1log_1_1Component.html#a146ce02cc7422b3a3bca07533536450e">Component::operator=</a>(Payload new_payload)</div>
<div class="line"><a id="l01735" name="l01735"></a><span class="lineno"> 1735</span>{</div>
<div class="line"><a id="l01736" name="l01736"></a><span class="lineno"> 1736</span>  <span class="keyword">static_assert</span>(std::is_enum_v&lt;Payload&gt;, <span class="stringliteral">&quot;Payload type must be an enum.&quot;</span>);</div>
<div class="line"><a id="l01737" name="l01737"></a><span class="lineno"> 1737</span>  <span class="keyword">static_assert</span>(std::is_same_v&lt;typename std::underlying_type_t&lt;Payload&gt;, <a class="code hl_typedef" href="classflow_1_1log_1_1Component.html#a287888e2943b312f4febc3e8e130fc80">enum_raw_t</a>&gt;,</div>
<div class="line"><a id="l01738" name="l01738"></a><span class="lineno"> 1738</span>                <span class="stringliteral">&quot;Payload enum underlying type must equal enum_raw_t.&quot;</span>);</div>
<div class="line"><a id="l01739" name="l01739"></a><span class="lineno"> 1739</span> </div>
<div class="line"><a id="l01740" name="l01740"></a><span class="lineno"> 1740</span>  <span class="comment">// Might be optimized-out to storing, essentially, a constant at the call site of this assignment (or ctor).</span></div>
<div class="line"><a id="l01741" name="l01741"></a><span class="lineno"> 1741</span>  <a class="code hl_variable" href="classflow_1_1log_1_1Component.html#a3c753f22e196c5f84718541ebb27dcac">m_payload_type_or_null</a> = &amp;(<span class="keyword">typeid</span>(Payload));</div>
<div class="line"><a id="l01742" name="l01742"></a><span class="lineno"> 1742</span>  <span class="comment">// Zero processor cycles (an `enum` value *is* internally its integer value).</span></div>
<div class="line"><a id="l01743" name="l01743"></a><span class="lineno"> 1743</span>  <a class="code hl_variable" href="classflow_1_1log_1_1Component.html#a5be216ad60f3e344a22151bdf4d8d8b6">m_payload_enum_raw_value</a> = <span class="keyword">static_cast&lt;</span><a class="code hl_typedef" href="classflow_1_1log_1_1Component.html#a287888e2943b312f4febc3e8e130fc80">enum_raw_t</a><span class="keyword">&gt;</span>(new_payload);</div>
<div class="line"><a id="l01744" name="l01744"></a><span class="lineno"> 1744</span> </div>
<div class="line"><a id="l01745" name="l01745"></a><span class="lineno"> 1745</span>  <span class="keywordflow">return</span> *<span class="keyword">this</span>;</div>
<div class="line"><a id="l01746" name="l01746"></a><span class="lineno"> 1746</span>}</div>
<div class="line"><a id="l01747" name="l01747"></a><span class="lineno"> 1747</span> </div>
<div class="line"><a id="l01748" name="l01748"></a><span class="lineno"> 1748</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> Component_payload&gt;</div>
<div class="line"><a id="l01749" name="l01749"></a><span class="lineno"><a class="line" href="classflow_1_1log_1_1Log__context.html#af1ac7f30ab442c3c6aa6079335df6c9a"> 1749</a></span><a class="code hl_function" href="classflow_1_1log_1_1Log__context.html#ae7100d2dd130d8f130e3e64fdb1f4fd9">Log_context::Log_context</a>(<a class="code hl_class" href="classflow_1_1log_1_1Logger.html">Logger</a>* logger, Component_payload component_payload) :</div>
<div class="line"><a id="l01750" name="l01750"></a><span class="lineno"> 1750</span>  m_logger(logger),</div>
<div class="line"><a id="l01751" name="l01751"></a><span class="lineno"> 1751</span>  m_component(component_payload)</div>
<div class="line"><a id="l01752" name="l01752"></a><span class="lineno"> 1752</span>{</div>
<div class="line"><a id="l01753" name="l01753"></a><span class="lineno"> 1753</span>  <span class="comment">// Nothing.</span></div>
<div class="line"><a id="l01754" name="l01754"></a><span class="lineno"> 1754</span>}</div>
<div class="line"><a id="l01755" name="l01755"></a><span class="lineno"> 1755</span> </div>
<div class="line"><a id="l01756" name="l01756"></a><span class="lineno"> 1756</span>} <span class="comment">// namespace flow::log</span></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html"><div class="ttname"><a href="classflow_1_1log_1_1Component.html">flow::log::Component</a></div><div class="ttdoc">A light-weight class, each object storing a component payload encoding an enum value from enum type o...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l00839">log.hpp:840</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html_a146ce02cc7422b3a3bca07533536450e"><div class="ttname"><a href="classflow_1_1log_1_1Component.html#a146ce02cc7422b3a3bca07533536450e">flow::log::Component::operator=</a></div><div class="ttdeci">Component &amp; operator=(const Component &amp;src)</div><div class="ttdoc">Overwrites *this with a copy of src.</div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html_a287888e2943b312f4febc3e8e130fc80"><div class="ttname"><a href="classflow_1_1log_1_1Component.html#a287888e2943b312f4febc3e8e130fc80">flow::log::Component::enum_raw_t</a></div><div class="ttdeci">unsigned int enum_raw_t</div><div class="ttdoc">The type Payload must be enum class Payload : enum_raw_t: an enum type encoded via this integer type.</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l00845">log.hpp:845</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html_a325e56b14d7ce51ea4ee3cdfe6189490"><div class="ttname"><a href="classflow_1_1log_1_1Component.html#a325e56b14d7ce51ea4ee3cdfe6189490">flow::log::Component::Component</a></div><div class="ttdeci">Component(Component &amp;&amp;src_moved)</div><div class="ttdoc">Constructs *this equal to src_moved.</div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html_a3c753f22e196c5f84718541ebb27dcac"><div class="ttname"><a href="classflow_1_1log_1_1Component.html#a3c753f22e196c5f84718541ebb27dcac">flow::log::Component::m_payload_type_or_null</a></div><div class="ttdeci">std::type_info const  * m_payload_type_or_null</div><div class="ttdoc">The typeid() of the Payload passed to the 1-arg constructor; if 0-arg ctor was used (empty() is true)...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01017">log.hpp:1017</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html_a3ff8ff4d75add447b3e10ded5430833d"><div class="ttname"><a href="classflow_1_1log_1_1Component.html#a3ff8ff4d75add447b3e10ded5430833d">flow::log::Component::payload_type</a></div><div class="ttdeci">const std::type_info &amp; payload_type() const</div><div class="ttdoc">Returns typeid(Payload), where Payload was the template param used when calling the originating one-a...</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00174">log.cpp:174</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html_a5af2f66731c407bd519a873706bd04c4"><div class="ttname"><a href="classflow_1_1log_1_1Component.html#a5af2f66731c407bd519a873706bd04c4">flow::log::Component::empty</a></div><div class="ttdeci">bool empty() const</div><div class="ttdoc">Returns true if *this is as if default-constructed (a null Component); false if as if constructed via...</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00169">log.cpp:169</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html_a5be216ad60f3e344a22151bdf4d8d8b6"><div class="ttname"><a href="classflow_1_1log_1_1Component.html#a5be216ad60f3e344a22151bdf4d8d8b6">flow::log::Component::m_payload_enum_raw_value</a></div><div class="ttdeci">enum_raw_t m_payload_enum_raw_value</div><div class="ttdoc">The internally stored integer representation of the enum value passed to the 1-arg constructor; meani...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01023">log.hpp:1023</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html_a5edb4c020c9de20e4c1c96c460b624e8"><div class="ttname"><a href="classflow_1_1log_1_1Component.html#a5edb4c020c9de20e4c1c96c460b624e8">flow::log::Component::Component</a></div><div class="ttdeci">Component(const Component &amp;src)</div><div class="ttdoc">Copies the source Component into *this.</div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html_a656f5868adbd8c58c493981fe1764699"><div class="ttname"><a href="classflow_1_1log_1_1Component.html#a656f5868adbd8c58c493981fe1764699">flow::log::Component::payload</a></div><div class="ttdeci">Payload payload() const</div><div class="ttdoc">Returns reference to immutable payload stored in *this; undefined behavior if empty() == true.</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01727">log.hpp:1727</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html_a78dc45840c6fb12bd53784f7ea277ab4"><div class="ttname"><a href="classflow_1_1log_1_1Component.html#a78dc45840c6fb12bd53784f7ea277ab4">flow::log::Component::operator=</a></div><div class="ttdeci">Component &amp; operator=(Component &amp;&amp;src_moved)</div><div class="ttdoc">Makes *this equal to src_moved.</div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html_a899a7d2b0c5daa8e4d666d431b9bf48e"><div class="ttname"><a href="classflow_1_1log_1_1Component.html#a899a7d2b0c5daa8e4d666d431b9bf48e">flow::log::Component::payload_enum_raw_value</a></div><div class="ttdeci">enum_raw_t payload_enum_raw_value() const</div><div class="ttdoc">Returns the numeric value of the enum payload stored by this Component, originating in the one-arg co...</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00180">log.cpp:180</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Component_html_a8c746035d0eea4a26d0982eabf63b713"><div class="ttname"><a href="classflow_1_1log_1_1Component.html#a8c746035d0eea4a26d0982eabf63b713">flow::log::Component::Component</a></div><div class="ttdeci">Component()</div><div class="ttdoc">Constructs a Component that stores no payload; meaning an unspecified-component Component that return...</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00158">log.cpp:158</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Log__context_html"><div class="ttname"><a href="classflow_1_1log_1_1Log__context.html">flow::log::Log_context</a></div><div class="ttdoc">Convenience class that simply stores a Logger and/or Component passed into a constructor; and returns...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01609">log.hpp:1610</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Log__context_html_a5c57a7f44959a01ca9a1c948a6686cc0"><div class="ttname"><a href="classflow_1_1log_1_1Log__context.html#a5c57a7f44959a01ca9a1c948a6686cc0">flow::log::Log_context::Log_context</a></div><div class="ttdeci">Log_context(const Log_context &amp;src)</div><div class="ttdoc">Copy constructor that stores equal Logger* and Component values as the source.</div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Log__context_html_a5d628315d5a93908d47a281980d3113e"><div class="ttname"><a href="classflow_1_1log_1_1Log__context.html#a5d628315d5a93908d47a281980d3113e">flow::log::Log_context::operator=</a></div><div class="ttdeci">Log_context &amp; operator=(const Log_context &amp;src)</div><div class="ttdoc">Assignment operator that behaves similarly to the copy constructor.</div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Log__context_html_a8a5fef42dc2cedf3c0d1a6e83beb2948"><div class="ttname"><a href="classflow_1_1log_1_1Log__context.html#a8a5fef42dc2cedf3c0d1a6e83beb2948">flow::log::Log_context::get_log_component</a></div><div class="ttdeci">const Component &amp; get_log_component() const</div><div class="ttdoc">Returns reference to the stored Component object, particularly as many FLOW_LOG_*() macros expect.</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00222">log.cpp:222</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Log__context_html_aa6bb8e4250586425631ef80063caf155"><div class="ttname"><a href="classflow_1_1log_1_1Log__context.html#aa6bb8e4250586425631ef80063caf155">flow::log::Log_context::swap</a></div><div class="ttdeci">void swap(Log_context &amp;other)</div><div class="ttdoc">Swaps Logger pointers and Component objects held by *this and other.</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00227">log.cpp:227</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Log__context_html_acf51230f139ac6f17748a02111b04086"><div class="ttname"><a href="classflow_1_1log_1_1Log__context.html#acf51230f139ac6f17748a02111b04086">flow::log::Log_context::m_component</a></div><div class="ttdeci">Component m_component</div><div class="ttdoc">The held Component object. Making the object non-const to allow operator=() to work.</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01712">log.hpp:1712</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Log__context_html_ae7100d2dd130d8f130e3e64fdb1f4fd9"><div class="ttname"><a href="classflow_1_1log_1_1Log__context.html#ae7100d2dd130d8f130e3e64fdb1f4fd9">flow::log::Log_context::Log_context</a></div><div class="ttdeci">Log_context(Logger *logger=0)</div><div class="ttdoc">Constructs Log_context by storing the given pointer to a Logger and a null Component.</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00188">log.cpp:188</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Log__context_html_af13297446a54d6d80eb33d8fc672c10f"><div class="ttname"><a href="classflow_1_1log_1_1Log__context.html#af13297446a54d6d80eb33d8fc672c10f">flow::log::Log_context::m_logger</a></div><div class="ttdeci">Logger * m_logger</div><div class="ttdoc">The held Logger pointer. Making the pointer itself non-const to allow operator=() to work.</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01710">log.hpp:1710</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Log__context_html_af4db395042b065b00398cd59845dcb4d"><div class="ttname"><a href="classflow_1_1log_1_1Log__context.html#af4db395042b065b00398cd59845dcb4d">flow::log::Log_context::get_logger</a></div><div class="ttdeci">Logger * get_logger() const</div><div class="ttdoc">Returns the stored Logger pointer, particularly as many FLOW_LOG_*() macros expect.</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00217">log.cpp:217</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Logger_html"><div class="ttname"><a href="classflow_1_1log_1_1Logger.html">flow::log::Logger</a></div><div class="ttdoc">Interface that the user should implement, passing the implementing Logger into logging classes (Flow'...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01280">log.hpp:1284</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Logger_html_a1ea9da10a13d3b422ba7162a13d7eeb1"><div class="ttname"><a href="classflow_1_1log_1_1Logger.html#a1ea9da10a13d3b422ba7162a13d7eeb1">flow::log::Logger::set_thread_info</a></div><div class="ttdeci">static void set_thread_info(std::string *call_thread_nickname, flow::util::Thread_id *call_thread_id)</div><div class="ttdoc">Same as set_thread_info_in_msg_metadata() but targets the given two variables as opposed to a Msg_met...</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00125">log.cpp:125</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Logger_html_a2d1a0283764e5f85abf00c7cee4c4e19"><div class="ttname"><a href="classflow_1_1log_1_1Logger.html#a2d1a0283764e5f85abf00c7cee4c4e19">flow::log::Logger::set_thread_info_in_msg_metadata</a></div><div class="ttdeci">static void set_thread_info_in_msg_metadata(Msg_metadata *msg_metadata)</div><div class="ttdoc">Loads msg_metadata-&gt;m_call_thread_nickname (if set) or else msg_metadata-&gt;m_call_thread_id,...</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00144">log.cpp:144</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Logger_html_a3e00a68f9086f1ef0f4e36b9f23f4d02"><div class="ttname"><a href="classflow_1_1log_1_1Logger.html#a3e00a68f9086f1ef0f4e36b9f23f4d02">flow::log::Logger::s_this_thread_nickname_ptr</a></div><div class="ttdeci">static boost::thread_specific_ptr&lt; std::string &gt; s_this_thread_nickname_ptr</div><div class="ttdoc">Thread-local storage for each thread's logged name (null pointer, which is default,...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01552">log.hpp:1552</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Logger_html_a5600c71ccaa294650c7d34b596d90bf5"><div class="ttname"><a href="classflow_1_1log_1_1Logger.html#a5600c71ccaa294650c7d34b596d90bf5">flow::log::Logger::this_thread_set_logged_nickname</a></div><div class="ttdeci">static void this_thread_set_logged_nickname(util::String_view thread_nickname=util::String_view(), Logger *logger_ptr=0, bool also_set_os_name=true)</div><div class="ttdoc">Sets or unsets the current thread's logging-worthy string name; optionally sets the OS thread name (s...</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00036">log.cpp:36</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Logger_html_a934667f16dd6ca0841e521296ab3a6e2"><div class="ttname"><a href="classflow_1_1log_1_1Logger.html#a934667f16dd6ca0841e521296ab3a6e2">flow::log::Logger::do_log</a></div><div class="ttdeci">virtual void do_log(Msg_metadata *metadata, util::String_view msg)=0</div><div class="ttdoc">Given a message and its severity, logs that message and possibly severity WITHOUT checking whether it...</div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Logger_html_a93541a6407b8705a76c7a161c5289b10"><div class="ttname"><a href="classflow_1_1log_1_1Logger.html#a93541a6407b8705a76c7a161c5289b10">flow::log::Logger::this_thread_logged_name_os_manip</a></div><div class="ttdeci">static std::ostream &amp; this_thread_logged_name_os_manip(std::ostream &amp;os)</div><div class="ttdoc">ostream manipulator function that, if output via operator&lt;&lt; to an ostream, will cause the current thr...</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00108">log.cpp:108</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Logger_html_ac8a2e7a33fe3fbc0c29ead62ed98c022"><div class="ttname"><a href="classflow_1_1log_1_1Logger.html#ac8a2e7a33fe3fbc0c29ead62ed98c022">flow::log::Logger::should_log</a></div><div class="ttdeci">virtual bool should_log(Sev sev, const Component &amp;component) const =0</div><div class="ttdoc">Given attributes of a hypothetical message that would be logged, return true if that message should b...</div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Logger_html_ad6ead44c19a7b15111b2f77656a2ea31"><div class="ttname"><a href="classflow_1_1log_1_1Logger.html#ad6ead44c19a7b15111b2f77656a2ea31">flow::log::Logger::this_thread_ostream</a></div><div class="ttdeci">std::ostream * this_thread_ostream() const</div><div class="ttdoc">Returns the stream dedicated to the executing thread and this Logger, so that the caller can apply st...</div><div class="ttdef"><b>Definition:</b> <a href="log_8cpp_source.html#l00150">log.cpp:150</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Logger_html_ae04868e2a384e60a349ecba8340cd731"><div class="ttname"><a href="classflow_1_1log_1_1Logger.html#ae04868e2a384e60a349ecba8340cd731">flow::log::Logger::logs_asynchronously</a></div><div class="ttdeci">virtual bool logs_asynchronously() const =0</div><div class="ttdoc">Must return true if do_log() at least sometimes logs the given message and metadata (e....</div></div>
<div class="ttc" id="aclassflow_1_1util_1_1Null__interface_html"><div class="ttname"><a href="classflow_1_1util_1_1Null__interface.html">flow::util::Null_interface</a></div><div class="ttdoc">An empty interface, consisting of nothing but a default virtual destructor, intended as a boiler-plat...</div><div class="ttdef"><b>Definition:</b> <a href="util_2util_8hpp_source.html#l00044">util.hpp:45</a></div></div>
<div class="ttc" id="aclassflow_1_1util_1_1Unique__id__holder_html"><div class="ttname"><a href="classflow_1_1util_1_1Unique__id__holder.html">flow::util::Unique_id_holder</a></div><div class="ttdoc">Each object of this class stores (at construction) and returns (on demand) a numeric ID unique from a...</div><div class="ttdef"><b>Definition:</b> <a href="uniq__id__holder_8hpp_source.html#l00106">uniq_id_holder.hpp:107</a></div></div>
<div class="ttc" id="adetail_2log__fwd_8hpp_html"><div class="ttname"><a href="detail_2log__fwd_8hpp.html">log_fwd.hpp</a></div></div>
<div class="ttc" id="alog__fwd_8hpp_html"><div class="ttname"><a href="log__fwd_8hpp.html">log_fwd.hpp</a></div></div>
<div class="ttc" id="anamespaceflow_1_1log_html"><div class="ttname"><a href="namespaceflow_1_1log.html">flow::log</a></div><div class="ttdoc">Flow module providing logging functionality.</div><div class="ttdef"><b>Definition:</b> <a href="async__file__logger_8cpp_source.html#l00027">async_file_logger.cpp:28</a></div></div>
<div class="ttc" id="anamespaceflow_1_1log_html_a5c602384e6fe9d7642740ac2fae4ad04"><div class="ttname"><a href="namespaceflow_1_1log.html#a5c602384e6fe9d7642740ac2fae4ad04">flow::log::Sev</a></div><div class="ttdeci">Sev</div><div class="ttdoc">Enumeration containing one of several message severity levels, ordered from highest to lowest.</div><div class="ttdef"><b>Definition:</b> <a href="log__fwd_8hpp_source.html#l00223">log_fwd.hpp:224</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html_a0a4e7b2d3107bd630e0dc0c0b8f2e4de"><div class="ttname"><a href="namespaceflow_1_1util.html#a0a4e7b2d3107bd630e0dc0c0b8f2e4de">flow::util::Thread_id</a></div><div class="ttdeci">Thread::id Thread_id</div><div class="ttdoc">Short-hand for an OS-provided ID of a util::Thread.</div><div class="ttdef"><b>Definition:</b> <a href="util__fwd_8hpp_source.html#l00090">util_fwd.hpp:90</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html_ae4dc52186797094b3040379ff19124c9"><div class="ttname"><a href="namespaceflow_1_1util.html#ae4dc52186797094b3040379ff19124c9">flow::util::String_view</a></div><div class="ttdeci">Basic_string_view&lt; char &gt; String_view</div><div class="ttdoc">Commonly used char-based Basic_string_view. See its doc header.</div><div class="ttdef"><b>Definition:</b> <a href="string__view_8hpp_source.html#l00191">string_view.hpp:191</a></div></div>
<div class="ttc" id="astructflow_1_1log_1_1Msg__metadata_html"><div class="ttname"><a href="structflow_1_1log_1_1Msg__metadata.html">flow::log::Msg_metadata</a></div><div class="ttdoc">Simple data store containing all of the information generated at every logging call site by flow::log...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01040">log.hpp:1041</a></div></div>
<div class="ttc" id="astructflow_1_1log_1_1Msg__metadata_html_a11e04fcee8409b76adb9aaa3108f90e1"><div class="ttname"><a href="structflow_1_1log_1_1Msg__metadata.html#a11e04fcee8409b76adb9aaa3108f90e1">flow::log::Msg_metadata::m_called_when</a></div><div class="ttdeci">std::chrono::system_clock::time_point m_called_when</div><div class="ttdoc">Time stamp from as close as possible to entry into the log call site (usually FLOW_LOG_WARNING() or s...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01112">log.hpp:1112</a></div></div>
<div class="ttc" id="astructflow_1_1log_1_1Msg__metadata_html_a278ef30d1bdceb9482c0aef097177c91"><div class="ttname"><a href="structflow_1_1log_1_1Msg__metadata.html#a278ef30d1bdceb9482c0aef097177c91">flow::log::Msg_metadata::m_call_thread_id</a></div><div class="ttdeci">util::Thread_id m_call_thread_id</div><div class="ttdoc">Thread ID of the thread from which the log call was invoked; or a default-constructed (no-thread) suc...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01137">log.hpp:1137</a></div></div>
<div class="ttc" id="astructflow_1_1log_1_1Msg__metadata_html_a2f17801fae328d1fdc070edc2578dd91"><div class="ttname"><a href="structflow_1_1log_1_1Msg__metadata.html#a2f17801fae328d1fdc070edc2578dd91">flow::log::Msg_metadata::m_msg_src_line</a></div><div class="ttdeci">unsigned int m_msg_src_line</div><div class="ttdoc">Copy of integer that would have come from built-in __LINE__ macro which is auto-invoked by all FLOW_L...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01102">log.hpp:1102</a></div></div>
<div class="ttc" id="astructflow_1_1log_1_1Msg__metadata_html_a38ed0fc480839dd1c177fa5a8d59368a"><div class="ttname"><a href="structflow_1_1log_1_1Msg__metadata.html#a38ed0fc480839dd1c177fa5a8d59368a">flow::log::Msg_metadata::m_msg_sev</a></div><div class="ttdeci">Sev m_msg_sev</div><div class="ttdoc">Severity of message, typically determined by choice of macro (e.g., FLOW_LOG_WARNING() vs.</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01051">log.hpp:1051</a></div></div>
<div class="ttc" id="astructflow_1_1log_1_1Msg__metadata_html_a4588cf8c827944e5379c6ad1fd11d6db"><div class="ttname"><a href="structflow_1_1log_1_1Msg__metadata.html#a4588cf8c827944e5379c6ad1fd11d6db">flow::log::Msg_metadata::m_call_thread_nickname</a></div><div class="ttdeci">std::string m_call_thread_nickname</div><div class="ttdoc">Thread nickname, as for Logger::this_thread_set_logged_nickname(), of the thread from which the log c...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01127">log.hpp:1127</a></div></div>
<div class="ttc" id="astructflow_1_1log_1_1Msg__metadata_html_a5e7224fd18f1b9b2600508ac399687dd"><div class="ttname"><a href="structflow_1_1log_1_1Msg__metadata.html#a5e7224fd18f1b9b2600508ac399687dd">flow::log::Msg_metadata::m_msg_src_file</a></div><div class="ttdeci">util::String_view m_msg_src_file</div><div class="ttdoc">Pointer/length into static-storage string that would have come from built-in __FILE__ macro which is ...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01096">log.hpp:1096</a></div></div>
<div class="ttc" id="astructflow_1_1log_1_1Msg__metadata_html_a9d966ba8a227d1e7af587a8191ccf934"><div class="ttname"><a href="structflow_1_1log_1_1Msg__metadata.html#a9d966ba8a227d1e7af587a8191ccf934">flow::log::Msg_metadata::m_msg_component</a></div><div class="ttdeci">Component m_msg_component</div><div class="ttdoc">Component of message, as of this writing coming from either Log_context constructor or FLOW_LOG_SET_C...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01045">log.hpp:1045</a></div></div>
<div class="ttc" id="astructflow_1_1log_1_1Msg__metadata_html_af7704a632434e7b52c43ab6047cf023b"><div class="ttname"><a href="structflow_1_1log_1_1Msg__metadata.html#af7704a632434e7b52c43ab6047cf023b">flow::log::Msg_metadata::m_msg_src_function</a></div><div class="ttdeci">util::String_view m_msg_src_function</div><div class="ttdoc">Analogous to m_msg_src_file but coming from __FUNCTION__, not __FILE__. See m_msg_src_file perf notes...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01105">log.hpp:1105</a></div></div>
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